# Ferroelectric Ceramic Materials Prepared by Nanoparticles in Outdoor Environmental Sculpture Art

Authors: Ning Zhang; Jiexu Li; Ying Xia
Journal: Advances in Materials Science and Engineering
 (2022)

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## Abstract

With the development and progress of the city, people’s research on outdoor sculpture has gone deeper, and the field of material research has been raised to the field of spiritual culture. Tang Sancai is beautiful in color and wonderful in shape, such that when ceramics are used in outdoor environmental sculpture art, except for its performance, its appearance and tone must also be taken into consideration. Even when ferroelectric ceramics are used in outdoor sculptures, changing their shapes and taking into account their colors can be done invisibly only by passing through an electromagnetic field. Ferroelectric ceramics are generally divided into insulating, dielectric, piezoelectric, magnetic, semiconductor, transparent, and infrared sensor ceramics. This article integrates the manufacturing method of ferroelectric ceramics into outdoor environmental sculpture art. First of all, this article describes the ferroelectric ceramics and outdoor environmental sculptures, explains the method of preparing ferroelectric ceramics from barium titanate nanoparticles, and explains the pyroelectric inverse process of the electric card effect principle of electric ceramic materials, the thermodynamics of Maxwell’s relationship, and the thermodynamics of Landau’s phenomenological theory. The elasticity of the system is calculated, and the preparation of tetragonal barium titanate ferroelectric ceramics prepared by hydrothermal nanoparticles and SBT/Cu ferroelectric ceramic composites prepared by nanoparticle metallurgy is explained. In the plasma discharge mode, the optimal temperature for sintering the composite material is obtained. Then through experiments, research on the preparation and performance of the high dielectric constant BTnf-Ag/PVDF ferroelectric ceramic nanocomposite and its application in environmental sculptures are demonstrated. Compared with the two ancient BTnf/PVDF composite materials, the barium titanate fiber prepared by electrostatic spinning shows that the BTnf-Ag/PVDF composite material has a higher dielectric constant, and the dielectric loss is not too high. The 41.8vol% BTnf-Ag composite material has a dielectric constant of 82.6BTnf/PVDF, but the composite material’s dielectric constant is only 62.4, an increase of 32%. The dielectric loss of the 41.8vol% BTnf-Ag composite material is 0.053, and the dielectric loss constant of the BTnf/PVDF composite material is 0.049; the dielectric loss is reduced by 8% year-on-year. Ferroelectric ceramic composites prepared by adding silver ions have ideal dielectric properties and enhanced energy storage density.


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## Body

## 1. Introduction

### 1.1. Background

With the continuous development of modern ceramic art, public art works with ceramics as the main material have emerged, and with the corrosion resistance of ceramic materials, they gradually show a scene of prosperity and development, and artworks no longer exist indoors. Decorations appear in the public environment with a brand-new image, and ingeniously integrate with the surrounding buildings, people, local historical changes, humanistic culture, etc., forming an artistic beauty with unique flavor. In outdoor environmental sculpture art, while there are requirements for materials, the pursuit of beauty is also out of control. These include beauty in form, beauty in color, beauty in space, and a sense of visual patchwork. In ancient times, when ceramics were made, the shape and color had already been made extremely. White is like jade, thin as paper, listening to sounds like qin, and viewing colors as clear. Even the exquisite glaze color cannot be exhausted in one book, and the exquisiteness is even more breathtaking. When aesthetics reaches a certain height, people want to combine science to move it to a higher level. As a result, when ferroelectric ceramics are produced, they want to explore them more, and nanoparticles are especially widely seen in the production of ferroelectric ceramics. Ferroelectric ceramics have properties that are not available in ceramics made by ancient methods. They combine light and effect to achieve the most vivid visual beauty. For example, when asked about the creation of an environmental sculpture in a myth, the flying Dunhuang fairy base needs to be placed with coils to achieve the effect of levitation, which is difficult for traditional ceramics. In ancient myths, the sun used by Kuafu to chase the day, the snake tail used by Nuwa to fill the sky, and the body of a bird filled by the sea by Jingwei, the pictures must express the majestic power and the charm of the fairy world, i.e., floating in the air is indispensable. The sense of floating can make use of the sense of space to form a patchwork landscape. In terms of color, the combination of magnetism and electricity can create visual illusions, and it can also be combined with electric field effects to create a sculpture form by itself, which is not bad.


### 1.2. Significance

This article is a useful exploration based on the preparation of ferroelectric ceramic materials from nanoparticles and their application in outdoor environmental sculptures. In the traditional process of preparing ceramics, although the shapes and colors are combined and the beauty is excellent, the development of science is destined to have a certain development in everything. This article is to increase the power of science on the basis of form and color, making it more unpredictable and visually stunning. In the experiment, the process of adding silver ions to barium titanate to prepare ferroelectric ceramics was proposed and observed, and conclusions were drawn. It is expected that ferroelectric ceramics can have better properties such as dielectric properties and energy storage density when preparing sculptures. Compared with the two ancient BTnf/PVDF composite materials, the barium titanate fiber prepared by electrospinning has a higher dielectric constant and the dielectric loss is not too high.


### 1.3. Related Work

Ferroelectric ceramics prepared by nanoparticles have excellent properties, and ferroelectric ceramics have a good development prospect in outdoor environmental sculptures. Various studies have been carried out one after another, in the hope that ferroelectric ceramics will be fully utilized in outdoor environmental sculpture art. Because the ceramic material is very special, especially the cultural background is relatively deep, sculptors like to use this material very much. AiY studied the casting of barium titanate nanopowders with an average particle size of 30 nm in different casting solvent systems (toluene-ethanol, methyl ethyl ketone-ethanol, xylene-ethanol). He also studied the dispersion performance of Tritonx-100 or phosphate as a dispersant. It was found that xylene-ethanol and phosphate were the best solvent and dispersant systems for casting. Using this system can form a defect-free, dense, smooth green belt [1]. HessienMM found that the precursor of the Ba-Sm-Ti mixture was thermally decomposed in a multi-step weight loss at a temperature of up to about 480°C, and the perovskite Ba0.85Sm0.1TiO3 began to form at about 520°C. X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy measurements show that the synthesized Ba0.85Sm0.1TiO3 has a tetragonal dominant structure. It has an intermediate SmTi2O3 at a lower annealing temperature. At higher annealing temperatures, the proportion of SmTi2O3 decreases and disappears completely [2]. Chen et al. found that under the condition of barium-titanium molar ratio of 1, microwave reaction at 80°C for 30 min, and calcination reaction at 700°C for 1 h, adding surfactant (OP-10) can prepare titanium with a diameter of about 50 nm and a c/a ratio of 1.0069 barium acid (BT) nanopowder. Microwave temperature and microwave time have a significant effect on the tetragonality of barium titanate nanopowders [3]. Afghahi et al. proposed an X-band microwave absorber design based on a ternary nanocomposite doped with barium hexaferrate (Ba-M)/calcium titanate (CTO)/multi-walled carbon nanotubes (MWCNT). The combination of these three components and their different loss mechanisms has a synergistic effect, which can enhance the attenuation characteristics of the final composite [4]. Li et al. observed a large electrothermal effect in La-doped (Bi0.5Na0.5) 0.94Ba0.06TiO3 lead-free ferroelectric ceramics synthesized by conventional solid-phase reaction. He measured the dielectric constant and ferromagnetic hysteresis loop, and used the indirect method to calculate the electrothermal temperature change of La-doped BNBT6. It is found that the introduction of La2O3 can enhance the electrothermal effect of BNBT6 [5]. Ma et al. studied the effect of La doping on the microstructure and electrical properties of 0.88PMN-0.12PT ceramics. All La-doped 0.88PMN-0.12PT ceramics exhibit a pure perovskite phase, with extremely dense microstructure and high light transmittance. Among them, the ceramic doped with 1.0 mol% La has the highest transparency in the near-infrared region, reaching about 70%. It is very close to its theoretical light transmittance and basically meets the requirements of electro-optical applications for light transmittance [6]. Won and Sang-Joo believe that the polarized lead zirconate titanate cuboid undergoes compressive stress loading and unloading, and after reaching a specific polarization, the stress is eliminated and the temperature is increased [7]. Although this article discusses the preparation of ferroelectric ceramics and its application in environmental sculptures, the dielectric properties of ferroelectric ceramics by barium titanate nanoparticles can be further studied, and we can find the optimal barium titanate nanoparticle diameter and optimal reducing ion.


### 1.4. Innovation

This article combines the method of preparing ferroelectric ceramics with barium titanate nanoparticles. The electric card effect principle of electric ceramic materials explains the inverse process of pyroelectricity, the thermodynamics of Maxwell’s relations, and the thermodynamics of Landau’s phenomenological theory. By calculating the elasticity of the system and preparing tetragonal barium titanate ferroelectric ceramics from nanoparticles by the hydrothermal method, SBT/Cu ferroelectric ceramic composites can be prepared by nanoparticle metallurgy. BaTiO3 nanofibers are prepared by high-voltage electrostatic spinning. BTnf-Ag is prepared by the chemical reduction method and used as a filler to prepare ferroelectric ceramic materials with excellent dielectric properties.


## 1.1. Background

With the continuous development of modern ceramic art, public art works with ceramics as the main material have emerged, and with the corrosion resistance of ceramic materials, they gradually show a scene of prosperity and development, and artworks no longer exist indoors. Decorations appear in the public environment with a brand-new image, and ingeniously integrate with the surrounding buildings, people, local historical changes, humanistic culture, etc., forming an artistic beauty with unique flavor. In outdoor environmental sculpture art, while there are requirements for materials, the pursuit of beauty is also out of control. These include beauty in form, beauty in color, beauty in space, and a sense of visual patchwork. In ancient times, when ceramics were made, the shape and color had already been made extremely. White is like jade, thin as paper, listening to sounds like qin, and viewing colors as clear. Even the exquisite glaze color cannot be exhausted in one book, and the exquisiteness is even more breathtaking. When aesthetics reaches a certain height, people want to combine science to move it to a higher level. As a result, when ferroelectric ceramics are produced, they want to explore them more, and nanoparticles are especially widely seen in the production of ferroelectric ceramics. Ferroelectric ceramics have properties that are not available in ceramics made by ancient methods. They combine light and effect to achieve the most vivid visual beauty. For example, when asked about the creation of an environmental sculpture in a myth, the flying Dunhuang fairy base needs to be placed with coils to achieve the effect of levitation, which is difficult for traditional ceramics. In ancient myths, the sun used by Kuafu to chase the day, the snake tail used by Nuwa to fill the sky, and the body of a bird filled by the sea by Jingwei, the pictures must express the majestic power and the charm of the fairy world, i.e., floating in the air is indispensable. The sense of floating can make use of the sense of space to form a patchwork landscape. In terms of color, the combination of magnetism and electricity can create visual illusions, and it can also be combined with electric field effects to create a sculpture form by itself, which is not bad.


## 1.2. Significance

This article is a useful exploration based on the preparation of ferroelectric ceramic materials from nanoparticles and their application in outdoor environmental sculptures. In the traditional process of preparing ceramics, although the shapes and colors are combined and the beauty is excellent, the development of science is destined to have a certain development in everything. This article is to increase the power of science on the basis of form and color, making it more unpredictable and visually stunning. In the experiment, the process of adding silver ions to barium titanate to prepare ferroelectric ceramics was proposed and observed, and conclusions were drawn. It is expected that ferroelectric ceramics can have better properties such as dielectric properties and energy storage density when preparing sculptures. Compared with the two ancient BTnf/PVDF composite materials, the barium titanate fiber prepared by electrospinning has a higher dielectric constant and the dielectric loss is not too high.


## 1.3. Related Work

Ferroelectric ceramics prepared by nanoparticles have excellent properties, and ferroelectric ceramics have a good development prospect in outdoor environmental sculptures. Various studies have been carried out one after another, in the hope that ferroelectric ceramics will be fully utilized in outdoor environmental sculpture art. Because the ceramic material is very special, especially the cultural background is relatively deep, sculptors like to use this material very much. AiY studied the casting of barium titanate nanopowders with an average particle size of 30 nm in different casting solvent systems (toluene-ethanol, methyl ethyl ketone-ethanol, xylene-ethanol). He also studied the dispersion performance of Tritonx-100 or phosphate as a dispersant. It was found that xylene-ethanol and phosphate were the best solvent and dispersant systems for casting. Using this system can form a defect-free, dense, smooth green belt [1]. HessienMM found that the precursor of the Ba-Sm-Ti mixture was thermally decomposed in a multi-step weight loss at a temperature of up to about 480°C, and the perovskite Ba0.85Sm0.1TiO3 began to form at about 520°C. X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy measurements show that the synthesized Ba0.85Sm0.1TiO3 has a tetragonal dominant structure. It has an intermediate SmTi2O3 at a lower annealing temperature. At higher annealing temperatures, the proportion of SmTi2O3 decreases and disappears completely [2]. Chen et al. found that under the condition of barium-titanium molar ratio of 1, microwave reaction at 80°C for 30 min, and calcination reaction at 700°C for 1 h, adding surfactant (OP-10) can prepare titanium with a diameter of about 50 nm and a c/a ratio of 1.0069 barium acid (BT) nanopowder. Microwave temperature and microwave time have a significant effect on the tetragonality of barium titanate nanopowders [3]. Afghahi et al. proposed an X-band microwave absorber design based on a ternary nanocomposite doped with barium hexaferrate (Ba-M)/calcium titanate (CTO)/multi-walled carbon nanotubes (MWCNT). The combination of these three components and their different loss mechanisms has a synergistic effect, which can enhance the attenuation characteristics of the final composite [4]. Li et al. observed a large electrothermal effect in La-doped (Bi0.5Na0.5) 0.94Ba0.06TiO3 lead-free ferroelectric ceramics synthesized by conventional solid-phase reaction. He measured the dielectric constant and ferromagnetic hysteresis loop, and used the indirect method to calculate the electrothermal temperature change of La-doped BNBT6. It is found that the introduction of La2O3 can enhance the electrothermal effect of BNBT6 [5]. Ma et al. studied the effect of La doping on the microstructure and electrical properties of 0.88PMN-0.12PT ceramics. All La-doped 0.88PMN-0.12PT ceramics exhibit a pure perovskite phase, with extremely dense microstructure and high light transmittance. Among them, the ceramic doped with 1.0 mol% La has the highest transparency in the near-infrared region, reaching about 70%. It is very close to its theoretical light transmittance and basically meets the requirements of electro-optical applications for light transmittance [6]. Won and Sang-Joo believe that the polarized lead zirconate titanate cuboid undergoes compressive stress loading and unloading, and after reaching a specific polarization, the stress is eliminated and the temperature is increased [7]. Although this article discusses the preparation of ferroelectric ceramics and its application in environmental sculptures, the dielectric properties of ferroelectric ceramics by barium titanate nanoparticles can be further studied, and we can find the optimal barium titanate nanoparticle diameter and optimal reducing ion.


## 1.4. Innovation

This article combines the method of preparing ferroelectric ceramics with barium titanate nanoparticles. The electric card effect principle of electric ceramic materials explains the inverse process of pyroelectricity, the thermodynamics of Maxwell’s relations, and the thermodynamics of Landau’s phenomenological theory. By calculating the elasticity of the system and preparing tetragonal barium titanate ferroelectric ceramics from nanoparticles by the hydrothermal method, SBT/Cu ferroelectric ceramic composites can be prepared by nanoparticle metallurgy. BaTiO3 nanofibers are prepared by high-voltage electrostatic spinning. BTnf-Ag is prepared by the chemical reduction method and used as a filler to prepare ferroelectric ceramic materials with excellent dielectric properties.


## 2. Nanoparticle Preparation Method of Ferroelectric Ceramic Materials

### 2.1. The Principle of the Electric Card Effect of Ferroelectric Ceramic Materials

In recent years, low-cost, high-efficiency, and environmentally friendly electro-card effect refrigeration materials have been widely studied, including inorganic perovskites, organic perovskites, organic polymers, molecular ferroelectric materials, and two-dimensional ferroelectric materials. The role of the electric card is to convert electricity into heat, which is the opposite process of thermoelectricity. The electric field causes the entropy of the ferroelectric ceramic material to change. In the absence of electric field interference, ferroelectric dipoles can move freely and have high dipole entropy, or system disturbances. Due to the interference of the electric field, the dipole is placed well. In other words, the entropy of the dipole is low. At this time, electrical energy is converted into thermal energy to generate heat. Then it eliminates electric field interference and absorbs heat from the outside. The heat dissipation cycle mechanism of the electric card is formed repeatedly [8]. The electrocaloric effect of a dielectric refers to the macroscopic thermodynamic quantities such as the heat capacity, temperature, and heat flux of the dielectric change under the action of the electrostatic field. The electrocaloric effect has many important applications. For example, the electrocaloric effect under the action of an electric field can be used to enhance the convective heat transfer process, and the temperature change of the dielectric under the action of an electric field can be used to design and manufacture refrigeration devices, which is why it has received widespread attention. Using Maxwell’s formula and Landau’s phase transition theory for reference, the thermodynamics of the electrocarding effect is explained from different angles, as shown in Figure 1.Figure 1
Schematic diagram of the electric card principle.


#### 2.1.1. Thermodynamic Explanation Based on the Maxwell Relationship

For ferroelectric ceramic materials, the system elasticity Gibbs free energy W can be expressed by the following differential equation:(1)dW=−SdT−fkdFk−DkdkEk.In this formula,S is the entropy, T is the absolute temperature, F is the stress, and E is the electric field strength. We can obtain(2)PWPEkF,T=−Dk,PWPTE,F=−S.Assuming that the function of free energyW is a continuous and derivable function, its second-order differential is expressed as(3)P2WPTPEkF=−PDkPTF,E=−PSPEkF,T.The above formula is the classic Maxwell formula. Based on this, it can be seen that the pyroelectric effect is thermodynamically equivalent to the electric card effect, andPDk/PTF,E is the pyroelectric coefficient. Under the conditions of constant stress and temperature, the entropy change of the system can be written as(4)dS=PSPEkF,TdEk=PDkPTF,EdEk.The isothermal entropy of the system after applying an electric field becomes(5)ΔS=∫EmEnPDPTF,EdE.Em and En represent the starting electric field and the ending electric field, respectively. Under the condition of the adiabatic environment and the stress unchanged, the entropy change relationship of the system is(6)dS=PSPETdE+PSPTEdT=0.LetCE=ρ,CE be the heat capacity per unit volume, CE be the specific heat capacity, and ρ represent its density; the unit is J/(k·m3).(7)CETdT=−PSPETdE=−PDPTE−dE.Em and En are marked as the initial electric field and the final electric field, respectively. If the adiabatic temperature increases, it is necessary to increase the thermoelectric coefficient and electric field strength, and reduce the specific heat capacity and density. In general, under the condition of ferroelectric phase change, the thermoelectric coefficient of ferroelectric materials is the highest. The electric field affects the temperature of the phase change of the material, which provides guidance for the preparation of high-performance electrical card heat dissipation materials. This equation only applies to continuous phase transitions; it does not apply to hysteresis effects [9].


#### 2.1.2. Thermodynamic Explanation Based on Landau’s Phenomenological Theory

To a certain extent, the Landau-Devonshire (L-D) phenomenological theory can explain the phase transition of most ferroelectric materials, i.e., it can be used to test the electrical card effect of electrical materials. The Gibbs free energyW of ferroelectric materials can be written as a polynomial with the order parameter X as the independent variable. Let X be a scalar; thus, the following expression can be obtained:(8)W=12aX2+14bX4+16cX6−EX.a=a0T−T0, b and c are used as phenomenological Landau coefficients, and generally do not affect the temperature. According to the thermodynamic formula dW=−SdT−fkdFk−DkdkEk, it can be known that PW/PTD,F=−S. In general, before and after applying an electric field (Em to En), the entropy change and adiabatic temperature change of the ferroelectric ceramic material under the isothermal bias field are, respectively:(9)ΔS=−12a0XEn,T2−XEm,T2,(10)ΔT=12CEa0TXEn,T2−XEm,T2,ΔT=−TΔSCE.It can be seen from the formula that when the external electric field acts on the ferroelectric material, the polarization of the system increases and the entropy of the system decreases. Moreover, according to the above formula, it can be seen that the change of the system entropy is proportional to the square of the polarization intensityP. Therefore, the greater influence of electrical interference mainly occurs near the period of the ferroelectric. Because there are many different forms of polarization [10], this formula will help find and design some high-performance electrical card heat dissipation materials.


### 2.2. Preparation of Tetragonal Barium Titanate from Nanoparticles by the Hydrothermal Method

Barium titanate is a ferroelectric compound material with high dielectric constant and low dielectric loss. It is one of the most widely used materials in electronic ceramics and is known as “the pillar of the electronic ceramics industry.” Hydrothermal synthesis uses water as the solvent in a closed container. By adding appropriate amounts of typical reactants and mineralizers, the hydrothermal reaction is carried out under a high-temperature and high-pressure environment. The characteristic of the hydrothermal method is that chemical reactions occur at higher temperatures and pressures, which makes these reactions impossible under conventional conditions. In the second step, the process is simple, the product is clean, the particle size is small, the distribution is narrow, and ideal stoichiometric materials can be obtained [11]. The product avoids the powdery form produced by the hydrothermal reaction, and it does not need to be heated during the heating process. It can reduce the abnormal growth and accumulation of dust inclusions and improve the sintering activity of the powder. The temperature of the hydrothermal reaction method is low, and a nano-level powder can be obtained. Therefore, the hydrothermal synthesis method is considered to be an ideal method that can promote the development of electronic components and the direction of chip miniaturization. Therefore, it is getting more and more attention. The hydrothermal reaction process refers to the general term for the relevant chemical reactions carried out in fluids such as water, aqueous solution, or steam under a certain temperature and pressure. According to the temperature of the hydrothermal reaction, it can be divided into subcritical reactions and supercritical reactions. The former reaction temperature is between 100 and 240°C, which is suitable for industrial or laboratory operations. At present, the industrial production of high-quality barium-titanium hydrothermal powder is adopting relevant methods. The principle is shown in Figure 2.Figure 2
Preparation process of tetragonal phase barium titanate.The chemical principle of the hydrothermal reaction is as follows.Before the hydrothermal reaction,(11)BaCH3COO2=Ba2++2CH3COO−,(12)TiOC4H94+H2O=C4H9O3TiOH+C4H9CH(13)C4H9O3TiOH+H2O=C4H9O2TiOH2+C4H9OH(14)C4H9O3TiOH2=C4H9OTiOH3+C4H9OH(15)C4H9OTiOH3+H2O=C4H9OTiOH3+C4H9OH(16)TiOH4+2OH−=TiOH62−In the hydrothermal reaction,(17)Ba2++TiOH62−=BaTiO3+3H2OThe hydrothermal formation of BaTiO3 follows the dissolution-precipitation mechanism, as shown in Figure 3.Figure 3
Formation mechanism of barium titanate particles.Then taking Ba(CH3COO)2 and Ti(C4H9O)4 as raw materials, the hydrothermal time is fixed at 60 hours, the KOH dosage is 1.5 mol/L, and the solvent ethanol content is 50%. At temperatures of 160°C, 180°C, 200°C, 220°C, and 240°C, five groups of BaTiO3 powders with different square crystal phase contents were obtained by the hydrothermal reaction. When the hydrothermal reaction time was extended from 60 hours to 90 hours, the c/lattice value of BaTiO3 gradually increased. The two diffraction peaks gradually increased to 45°, and the tetragonal crystal content increased from 64.3% to 81.6%. When the hydrothermal reaction time reaches 100 hours, the diffraction peak is 0.435, the c/value is 1,0001, and the tetragonal period is 84.1%. This indicates that the hydrothermal reaction time is sufficiently increased, so that the tetragonal phase can increase the content of BaTiO3 powder. In order to determine the tetragonal phase content of BaTiO3 powder, XRD tests were performed on the five groups of powders, and the XRD test results obtained are shown in Figure 4.Figure 4
XRD patterns of BaTiO3 synthesized at different reaction temperatures and different hydrothermal reaction times.If the solution is very alkaline and sufficient temperature is observed for the hydrothermal reaction, the resulting tetragonal product BaTiO3 will still have a cubic phase. It can be said that the hydrothermal method cannot produce a complete BaTiO3 tetragonal product [12]. Hyun-Wook Lee et al. used Ba(OH)2·H2O and Ti[O(CH2)3·CH3]4 as raw materials. EDA and TEA are solvents for preparing nanometer-scale tetragonal BaTiO3. It has been found that two defects reduce the content of tetragonal BaTiO3, namely the OH- defects in the nanoparticles and the cubic shell on the surface of the BaTiO3 particles. According to the above results, as the hydrothermal temperature and hydrothermal time increase, barium titanate changes from a metastable cubic phase to a tetragonal phase.


### 2.3. Preparation of Sbt/Cu Ferroelectric Ceramic Composites by Powder Metallurgy

The powder metallurgy process starts from the preparation of powder raw materials. These powder raw materials can be pure metals or compounds. There are many methods for producing powders. The particle size, shape, bulk density, chemical composition, compressibility related to the subsequent molding process, sinterability, etc. all depend on the milling process route. In this paper, powder metallurgy is used to prepare SBT/Cu composite materials. The preparation process includes nodular ball mill, cold press, and sintering. Finally, SBT ceramic-reinforced copper-based composite materials and PT ceramic-reinforced copper-based composite materials are prepared to obtain sintered composite materials. The green body is then cut and tested. There are two sintering methods, vacuum hot pressing sintering and spark plasma sintering. The specific preparation process of the composite material is as follows:(1)
The first step in mixing powders to prepare metal matrix composites is to mix the matrix and the reinforcing materials uniformly. Because the density of reinforced SBT ceramics and PT ceramics is very different from the density of base Cu, the planetary ball milling method is used to mix the powders. Use alcohol as a medium to prevent Cu powder from being oxidized by the indoor heating ball mill process [13]. Ball milling process: ball-to-material ratio 2 : 1; ball milling speed 300r/min. The ball milling time is 12 hours, and the ball milling equipment is a QM-1SP (ZL) planetary ball mill produced by Nanjing University Instrument Factory. The ball milling tank is corundum tank, with ZrO2 ball.(2)
Cold pressing is to cold press the mixed powder before sintering. Pour the mixed powder into a graphite mold and press it into the mold unilaterally to make it have a certain strength. Cold pressing helps remove the gas absorbed in the powder. The cold pressing pressure should not be too high, and part of the gas is trapped by dust and cannot be discharged, which will eventually lead to composite pores and affect the performance of the composite materials [14].(3)
This article uses two methods to sinter composite materials, namely spark plasma sintering and vacuum hot pressing sintering. According to the two sintering methods, the sintering process is shown in Table1.Table 1
Sintering process of ferroelectric ceramic composite materials.
Vacuum hot pressing sinteringElectric spark sinteringHeating rate11°C/min52°C/minSintering temperature948°C652°CSintering pressure50 MPa50 MPaHolding time131 min12 minVacuum0.001 Pa0.1 PaVacuum hot press sintering uses thermal diffusion to heat the composite material. Since the temperature of the entire sintering furnace is the same, the sintering temperature is 948°C, which is slightly lower than the melting point of the general sintering temperature Cu. The spark plasma sintering method uses a large pulse current to pass the composite powder to achieve the purpose of rapid heating. The heating speed is faster. Since the temperature measurement point inside the equipment is on the outer surface of the mold, the core temperature of the mold is higher than the surface temperature of the tested mold. According to actual tests, the sintering temperature of 652°C is the best temperature for sintering Cu-based composite materials. Due to the different sintering mechanism, the sintering time required for spark plasma sintering is much shorter than the time required for hot pressing sintering. The gas in the powder is quickly discharged through the discharge plasma heating method from the inside to the outside, and the gas flow is guided from the inside to the outside. The requirements for vacuum hot pressing sintering equipment are lower than those for vacuum hot pressing sintering equipment, because the composite material sintered on the core is basically not affected by the air outside the mold [15].


## 2.1. The Principle of the Electric Card Effect of Ferroelectric Ceramic Materials

In recent years, low-cost, high-efficiency, and environmentally friendly electro-card effect refrigeration materials have been widely studied, including inorganic perovskites, organic perovskites, organic polymers, molecular ferroelectric materials, and two-dimensional ferroelectric materials. The role of the electric card is to convert electricity into heat, which is the opposite process of thermoelectricity. The electric field causes the entropy of the ferroelectric ceramic material to change. In the absence of electric field interference, ferroelectric dipoles can move freely and have high dipole entropy, or system disturbances. Due to the interference of the electric field, the dipole is placed well. In other words, the entropy of the dipole is low. At this time, electrical energy is converted into thermal energy to generate heat. Then it eliminates electric field interference and absorbs heat from the outside. The heat dissipation cycle mechanism of the electric card is formed repeatedly [8]. The electrocaloric effect of a dielectric refers to the macroscopic thermodynamic quantities such as the heat capacity, temperature, and heat flux of the dielectric change under the action of the electrostatic field. The electrocaloric effect has many important applications. For example, the electrocaloric effect under the action of an electric field can be used to enhance the convective heat transfer process, and the temperature change of the dielectric under the action of an electric field can be used to design and manufacture refrigeration devices, which is why it has received widespread attention. Using Maxwell’s formula and Landau’s phase transition theory for reference, the thermodynamics of the electrocarding effect is explained from different angles, as shown in Figure 1.Figure 1
Schematic diagram of the electric card principle.


### 2.1.1. Thermodynamic Explanation Based on the Maxwell Relationship

For ferroelectric ceramic materials, the system elasticity Gibbs free energy W can be expressed by the following differential equation:(1)dW=−SdT−fkdFk−DkdkEk.In this formula,S is the entropy, T is the absolute temperature, F is the stress, and E is the electric field strength. We can obtain(2)PWPEkF,T=−Dk,PWPTE,F=−S.Assuming that the function of free energyW is a continuous and derivable function, its second-order differential is expressed as(3)P2WPTPEkF=−PDkPTF,E=−PSPEkF,T.The above formula is the classic Maxwell formula. Based on this, it can be seen that the pyroelectric effect is thermodynamically equivalent to the electric card effect, andPDk/PTF,E is the pyroelectric coefficient. Under the conditions of constant stress and temperature, the entropy change of the system can be written as(4)dS=PSPEkF,TdEk=PDkPTF,EdEk.The isothermal entropy of the system after applying an electric field becomes(5)ΔS=∫EmEnPDPTF,EdE.Em and En represent the starting electric field and the ending electric field, respectively. Under the condition of the adiabatic environment and the stress unchanged, the entropy change relationship of the system is(6)dS=PSPETdE+PSPTEdT=0.LetCE=ρ,CE be the heat capacity per unit volume, CE be the specific heat capacity, and ρ represent its density; the unit is J/(k·m3).(7)CETdT=−PSPETdE=−PDPTE−dE.Em and En are marked as the initial electric field and the final electric field, respectively. If the adiabatic temperature increases, it is necessary to increase the thermoelectric coefficient and electric field strength, and reduce the specific heat capacity and density. In general, under the condition of ferroelectric phase change, the thermoelectric coefficient of ferroelectric materials is the highest. The electric field affects the temperature of the phase change of the material, which provides guidance for the preparation of high-performance electrical card heat dissipation materials. This equation only applies to continuous phase transitions; it does not apply to hysteresis effects [9].


### 2.1.2. Thermodynamic Explanation Based on Landau’s Phenomenological Theory

To a certain extent, the Landau-Devonshire (L-D) phenomenological theory can explain the phase transition of most ferroelectric materials, i.e., it can be used to test the electrical card effect of electrical materials. The Gibbs free energyW of ferroelectric materials can be written as a polynomial with the order parameter X as the independent variable. Let X be a scalar; thus, the following expression can be obtained:(8)W=12aX2+14bX4+16cX6−EX.a=a0T−T0, b and c are used as phenomenological Landau coefficients, and generally do not affect the temperature. According to the thermodynamic formula dW=−SdT−fkdFk−DkdkEk, it can be known that PW/PTD,F=−S. In general, before and after applying an electric field (Em to En), the entropy change and adiabatic temperature change of the ferroelectric ceramic material under the isothermal bias field are, respectively:(9)ΔS=−12a0XEn,T2−XEm,T2,(10)ΔT=12CEa0TXEn,T2−XEm,T2,ΔT=−TΔSCE.It can be seen from the formula that when the external electric field acts on the ferroelectric material, the polarization of the system increases and the entropy of the system decreases. Moreover, according to the above formula, it can be seen that the change of the system entropy is proportional to the square of the polarization intensityP. Therefore, the greater influence of electrical interference mainly occurs near the period of the ferroelectric. Because there are many different forms of polarization [10], this formula will help find and design some high-performance electrical card heat dissipation materials.


## 2.1.1. Thermodynamic Explanation Based on the Maxwell Relationship

For ferroelectric ceramic materials, the system elasticity Gibbs free energy W can be expressed by the following differential equation:(1)dW=−SdT−fkdFk−DkdkEk.In this formula,S is the entropy, T is the absolute temperature, F is the stress, and E is the electric field strength. We can obtain(2)PWPEkF,T=−Dk,PWPTE,F=−S.Assuming that the function of free energyW is a continuous and derivable function, its second-order differential is expressed as(3)P2WPTPEkF=−PDkPTF,E=−PSPEkF,T.The above formula is the classic Maxwell formula. Based on this, it can be seen that the pyroelectric effect is thermodynamically equivalent to the electric card effect, andPDk/PTF,E is the pyroelectric coefficient. Under the conditions of constant stress and temperature, the entropy change of the system can be written as(4)dS=PSPEkF,TdEk=PDkPTF,EdEk.The isothermal entropy of the system after applying an electric field becomes(5)ΔS=∫EmEnPDPTF,EdE.Em and En represent the starting electric field and the ending electric field, respectively. Under the condition of the adiabatic environment and the stress unchanged, the entropy change relationship of the system is(6)dS=PSPETdE+PSPTEdT=0.LetCE=ρ,CE be the heat capacity per unit volume, CE be the specific heat capacity, and ρ represent its density; the unit is J/(k·m3).(7)CETdT=−PSPETdE=−PDPTE−dE.Em and En are marked as the initial electric field and the final electric field, respectively. If the adiabatic temperature increases, it is necessary to increase the thermoelectric coefficient and electric field strength, and reduce the specific heat capacity and density. In general, under the condition of ferroelectric phase change, the thermoelectric coefficient of ferroelectric materials is the highest. The electric field affects the temperature of the phase change of the material, which provides guidance for the preparation of high-performance electrical card heat dissipation materials. This equation only applies to continuous phase transitions; it does not apply to hysteresis effects [9].


## 2.1.2. Thermodynamic Explanation Based on Landau’s Phenomenological Theory

To a certain extent, the Landau-Devonshire (L-D) phenomenological theory can explain the phase transition of most ferroelectric materials, i.e., it can be used to test the electrical card effect of electrical materials. The Gibbs free energyW of ferroelectric materials can be written as a polynomial with the order parameter X as the independent variable. Let X be a scalar; thus, the following expression can be obtained:(8)W=12aX2+14bX4+16cX6−EX.a=a0T−T0, b and c are used as phenomenological Landau coefficients, and generally do not affect the temperature. According to the thermodynamic formula dW=−SdT−fkdFk−DkdkEk, it can be known that PW/PTD,F=−S. In general, before and after applying an electric field (Em to En), the entropy change and adiabatic temperature change of the ferroelectric ceramic material under the isothermal bias field are, respectively:(9)ΔS=−12a0XEn,T2−XEm,T2,(10)ΔT=12CEa0TXEn,T2−XEm,T2,ΔT=−TΔSCE.It can be seen from the formula that when the external electric field acts on the ferroelectric material, the polarization of the system increases and the entropy of the system decreases. Moreover, according to the above formula, it can be seen that the change of the system entropy is proportional to the square of the polarization intensityP. Therefore, the greater influence of electrical interference mainly occurs near the period of the ferroelectric. Because there are many different forms of polarization [10], this formula will help find and design some high-performance electrical card heat dissipation materials.


## 2.2. Preparation of Tetragonal Barium Titanate from Nanoparticles by the Hydrothermal Method

Barium titanate is a ferroelectric compound material with high dielectric constant and low dielectric loss. It is one of the most widely used materials in electronic ceramics and is known as “the pillar of the electronic ceramics industry.” Hydrothermal synthesis uses water as the solvent in a closed container. By adding appropriate amounts of typical reactants and mineralizers, the hydrothermal reaction is carried out under a high-temperature and high-pressure environment. The characteristic of the hydrothermal method is that chemical reactions occur at higher temperatures and pressures, which makes these reactions impossible under conventional conditions. In the second step, the process is simple, the product is clean, the particle size is small, the distribution is narrow, and ideal stoichiometric materials can be obtained [11]. The product avoids the powdery form produced by the hydrothermal reaction, and it does not need to be heated during the heating process. It can reduce the abnormal growth and accumulation of dust inclusions and improve the sintering activity of the powder. The temperature of the hydrothermal reaction method is low, and a nano-level powder can be obtained. Therefore, the hydrothermal synthesis method is considered to be an ideal method that can promote the development of electronic components and the direction of chip miniaturization. Therefore, it is getting more and more attention. The hydrothermal reaction process refers to the general term for the relevant chemical reactions carried out in fluids such as water, aqueous solution, or steam under a certain temperature and pressure. According to the temperature of the hydrothermal reaction, it can be divided into subcritical reactions and supercritical reactions. The former reaction temperature is between 100 and 240°C, which is suitable for industrial or laboratory operations. At present, the industrial production of high-quality barium-titanium hydrothermal powder is adopting relevant methods. The principle is shown in Figure 2.Figure 2
Preparation process of tetragonal phase barium titanate.The chemical principle of the hydrothermal reaction is as follows.Before the hydrothermal reaction,(11)BaCH3COO2=Ba2++2CH3COO−,(12)TiOC4H94+H2O=C4H9O3TiOH+C4H9CH(13)C4H9O3TiOH+H2O=C4H9O2TiOH2+C4H9OH(14)C4H9O3TiOH2=C4H9OTiOH3+C4H9OH(15)C4H9OTiOH3+H2O=C4H9OTiOH3+C4H9OH(16)TiOH4+2OH−=TiOH62−In the hydrothermal reaction,(17)Ba2++TiOH62−=BaTiO3+3H2OThe hydrothermal formation of BaTiO3 follows the dissolution-precipitation mechanism, as shown in Figure 3.Figure 3
Formation mechanism of barium titanate particles.Then taking Ba(CH3COO)2 and Ti(C4H9O)4 as raw materials, the hydrothermal time is fixed at 60 hours, the KOH dosage is 1.5 mol/L, and the solvent ethanol content is 50%. At temperatures of 160°C, 180°C, 200°C, 220°C, and 240°C, five groups of BaTiO3 powders with different square crystal phase contents were obtained by the hydrothermal reaction. When the hydrothermal reaction time was extended from 60 hours to 90 hours, the c/lattice value of BaTiO3 gradually increased. The two diffraction peaks gradually increased to 45°, and the tetragonal crystal content increased from 64.3% to 81.6%. When the hydrothermal reaction time reaches 100 hours, the diffraction peak is 0.435, the c/value is 1,0001, and the tetragonal period is 84.1%. This indicates that the hydrothermal reaction time is sufficiently increased, so that the tetragonal phase can increase the content of BaTiO3 powder. In order to determine the tetragonal phase content of BaTiO3 powder, XRD tests were performed on the five groups of powders, and the XRD test results obtained are shown in Figure 4.Figure 4
XRD patterns of BaTiO3 synthesized at different reaction temperatures and different hydrothermal reaction times.If the solution is very alkaline and sufficient temperature is observed for the hydrothermal reaction, the resulting tetragonal product BaTiO3 will still have a cubic phase. It can be said that the hydrothermal method cannot produce a complete BaTiO3 tetragonal product [12]. Hyun-Wook Lee et al. used Ba(OH)2·H2O and Ti[O(CH2)3·CH3]4 as raw materials. EDA and TEA are solvents for preparing nanometer-scale tetragonal BaTiO3. It has been found that two defects reduce the content of tetragonal BaTiO3, namely the OH- defects in the nanoparticles and the cubic shell on the surface of the BaTiO3 particles. According to the above results, as the hydrothermal temperature and hydrothermal time increase, barium titanate changes from a metastable cubic phase to a tetragonal phase.


## 2.3. Preparation of Sbt/Cu Ferroelectric Ceramic Composites by Powder Metallurgy

The powder metallurgy process starts from the preparation of powder raw materials. These powder raw materials can be pure metals or compounds. There are many methods for producing powders. The particle size, shape, bulk density, chemical composition, compressibility related to the subsequent molding process, sinterability, etc. all depend on the milling process route. In this paper, powder metallurgy is used to prepare SBT/Cu composite materials. The preparation process includes nodular ball mill, cold press, and sintering. Finally, SBT ceramic-reinforced copper-based composite materials and PT ceramic-reinforced copper-based composite materials are prepared to obtain sintered composite materials. The green body is then cut and tested. There are two sintering methods, vacuum hot pressing sintering and spark plasma sintering. The specific preparation process of the composite material is as follows:(1)
The first step in mixing powders to prepare metal matrix composites is to mix the matrix and the reinforcing materials uniformly. Because the density of reinforced SBT ceramics and PT ceramics is very different from the density of base Cu, the planetary ball milling method is used to mix the powders. Use alcohol as a medium to prevent Cu powder from being oxidized by the indoor heating ball mill process [13]. Ball milling process: ball-to-material ratio 2 : 1; ball milling speed 300r/min. The ball milling time is 12 hours, and the ball milling equipment is a QM-1SP (ZL) planetary ball mill produced by Nanjing University Instrument Factory. The ball milling tank is corundum tank, with ZrO2 ball.(2)
Cold pressing is to cold press the mixed powder before sintering. Pour the mixed powder into a graphite mold and press it into the mold unilaterally to make it have a certain strength. Cold pressing helps remove the gas absorbed in the powder. The cold pressing pressure should not be too high, and part of the gas is trapped by dust and cannot be discharged, which will eventually lead to composite pores and affect the performance of the composite materials [14].(3)
This article uses two methods to sinter composite materials, namely spark plasma sintering and vacuum hot pressing sintering. According to the two sintering methods, the sintering process is shown in Table1.Table 1
Sintering process of ferroelectric ceramic composite materials.
Vacuum hot pressing sinteringElectric spark sinteringHeating rate11°C/min52°C/minSintering temperature948°C652°CSintering pressure50 MPa50 MPaHolding time131 min12 minVacuum0.001 Pa0.1 PaVacuum hot press sintering uses thermal diffusion to heat the composite material. Since the temperature of the entire sintering furnace is the same, the sintering temperature is 948°C, which is slightly lower than the melting point of the general sintering temperature Cu. The spark plasma sintering method uses a large pulse current to pass the composite powder to achieve the purpose of rapid heating. The heating speed is faster. Since the temperature measurement point inside the equipment is on the outer surface of the mold, the core temperature of the mold is higher than the surface temperature of the tested mold. According to actual tests, the sintering temperature of 652°C is the best temperature for sintering Cu-based composite materials. Due to the different sintering mechanism, the sintering time required for spark plasma sintering is much shorter than the time required for hot pressing sintering. The gas in the powder is quickly discharged through the discharge plasma heating method from the inside to the outside, and the gas flow is guided from the inside to the outside. The requirements for vacuum hot pressing sintering equipment are lower than those for vacuum hot pressing sintering equipment, because the composite material sintered on the core is basically not affected by the air outside the mold [15].


## 3. The Preparation and Performance of High Dielectric Constant Btnf-Ag/Pvdf Ferroelectric Ceramic Nanocomposite and Its Application in Environmental Sculptures

This article will describe the core-shell structure of the barium-titanium-silver hybrid fiber. This effectively increases the polarization interface and reduces the ability of the polymer to transfer internal loads. The barium-titanium fiber is the core of this structure, and the nano-silver particles adhere to the surface of the fiber to play the role of the clay structure. In the electric field, the polarization of a single particle forms a nano-silver microcapacitor. It can be added to different loads to effectively increase the charge polarization and form the Coulomb block effect [16]. Adding this core-shell structured filler to the polymer can effectively limit the transfer of electric charges from the inside of the composite material, thereby having the effect of increasing the dielectric constant. In addition, the Coulomb effect of these metallic silver particles improves the fracture strength and the overall performance of the composite material. The Coulomb effect is a fundamental charge-related interaction in nature, which is ubiquitous in fields such as physics, chemistry, and biology.


### 3.1. Experiment Part

Dissolve the prepared barium-titanium nanofiber fixed power supply in 300 ml of absolute ethanol, and ultrasonically mix for 5 minutes until a uniform and stable white emulsion is obtained. The white emulsion was prepared and precipitated at 800 r/min and transferred to an oven at 70°C for 10 hours. The white powder was used as the raw material for the next experiment. Weigh out the barium titanate wire and silver nitrate according to the ratio of 2.0 g barium titanate and 0.2 g silver nitrate. Add 300 ml of ethylene glycol solution and mix for 30 minutes until the solution becomes a red emulsion after 5 minutes of sonication. The emulsion was transferred to a glass in a three-necked vial, and then transferred to a heating bath mixed with magnetic oil. Carefully arrange the reaction and keep it for 20 minutes when the temperature reaches 130°C. The color of the final solution was brown, indicating the formation of silver nanoparticles. After the reaction was completed, the three-necked balloon was taken out of the oil bath and cooled to room temperature naturally. After discarding the separate emulsion, the bottom layer was centrifuged and mixed, washed with ethanol solution for 3–5 times, and then the precipitate was transferred to a drying box for 24 hours to obtain BTnf. Using a hybrid optical fiber substitute instead of -ag, weigh BTnf-Ag and PVDF powder in a prescribed manner at room temperature, and dissolve PVDF in a certain amount of DMF. Ultrasonic mixing was performed at 40°C for 30 minutes, and the BTnf-Ag powder used for the above-mentioned purposes was spined out. Melt in the mixture and stir in the ultrasonic solution for 15 minutes. The resulting mixture was then coated in a clean glass dish, and then transferred to a drying oven at 70°C for 12 hours. Finally, the composite screen is quickly heated to 180°C. Immediately immerse in ice water, remove from the composite glass screen, and dry at 40°C for 12 hours. We can understand that Ag+ can be reduced to Ag nanoparticles in the solution, and because the silver particles are discretely dispersed on the surface of the titanium-barium fiber, we can understand that the silver nanoparticles are successfully loaded on the surface of the fiber, as shown in Figure5.Figure 5
X-ray photoelectron spectra of BTnf and BTnf-Ag Ag3d3/2.SEM, XRD, XPS, etc., have verified that the silver nanoparticles have been successfully reduced, and the silver nanoparticles are dispersed on the surface of the titanium barium fiber. The change of nano-silver-barium-titanium has a significant effect on improving the polymer interface structure, and it improves the spleen. They are assembled in the distribution of internal materials to reduce the surface porosity of the composite material and prepare alternative materials for testing the dielectric properties of the composite material.


### 3.2. Study on the Dielectric Properties of the Btnf-Ag/Pvdf Composite

We first prepared samples with different component contents according to the fixed ratio of BTnf-Ag and PVDF. We use the formula to calculate the contents of BTnf-Ag(wt), BTnf-Ag(vol), BTnf(vol), and Ag(vo) in the barium-titanium nanofiber sample, as shown in Table2.Table 2
The content of each component in the BTnf-Ag/PVDF hybrid particles.
SampleBTnf-Ag (wt)BTnf-Ag (vol)BTnf (vol)Ag (vol)ɛ/δ (1 kHz)ɛ/δ (100 KHz)PVDF000014.2/0.01513.2/0.057BTnf-Ag/PVDF-124.17.452.421.4/0.01819.9/0.060BTnf-Ag/PVDF-240.214.8104.829.3/0.03027.3/0.059BTnf-Ag/PVDF-360.728.3208.343.3/0.03639.9/0.060BTnf-Ag/PVDF-474.941.83011.882.6/0.04273.8/0.055BTnf-Ag/PVDF-584.355.74015.798.1/0.04989.1/0.049It can be seen from Figure6 that in the range of 1 kHz∼105 Hz, when the content of BTnf-Ag is less than 28.3vol%, the dielectric constant of the BTnf-Ag composite material has a small change, i.e., the dielectric constant. It is a composite material with relatively independent frequency. The main reason is that at relatively low frequencies, the dielectric constant has a weaker relaxation effect on the composite material and has a small contribution to the dielectric constant. At the same time, the dielectric constant at low frequencies is relatively low. The main reason is that the relative content of BTnf-Ag (the dielectric constant of BaTiO3) is much higher than that of the PVDF polymer matrix, which is the dielectric constant [17]. When the content of BTnf-Ag exceeds 27.3vol%, especially when the content reaches 41.8vol%, and the filler increases by a certain amount, the contact probability of the filler surface inside the composite material increases significantly. Moreover, the Ag particles also enhance the interface polarization. The increase in the electrical constant is greater, and the change in the direction of the positive and negative poles at the center of the dipole moment cannot keep up with the change in the direction of the electric field. Another reason is that the dielectric properties of the filler and the matrix are so different that their ability to trap carriers and electrons in the composite is also different. Increasing the content greatly increases the chance of contact between fillers and increases their frequency. With the increase in the dipole moment, it cannot keep up with the rhythm of the electric field change, the polarizability drops sharply, and the dielectric constant drops significantly [18]. The results show that the continuous dielectric constant will decrease with the increase, and the change of the content product is more obvious.Figure 6
Frequency dependence of the dielectric constant and the dielectric loss of PVDF nanocomposites with different contents of BTnf-Ag and BTnf.When the material is low, the impact frequency on the dielectric loss is small. For example, in the range of 1 kHz to 10 kHz, for 7.4vol% of BTnf-Ag, it can be seen that the dielectric loss of the composite material can be reduced from 0.023 to about 0.021. As the content gradually increases, the dielectric loss of the composite material also increases. For example, in the range of 1 kHz to 10 kHz, when the BTnf-Ag content is 14.8vol%, it can be seen that the dielectric loss of the composite material is reduced from 0.061 to about 0.032. But in the range of 10 kHz to 1 MHz, the dielectric loss first increases and then decreases, and peaks appear. The reason may be that the movement of carriers is blocked, the BTnf-Ag dipole orientation releases polarization, and the material orientation does not follow the polarization. The change in the electric field leads to a higher hysteresis. The polarization formation and transformation of the molecular electric field leads to the loss of molecular chains and increases the energy loss [19]. In the range of 106 to 107 Hz, as the electric field changes, the polarization of the medium cannot continue, the current increases, and a wave crest appears. The introduction of Ag nanoparticles can significantly increase the dielectric constant, while the dielectric loss slightly increases. For example, the dielectric constant of the composite material is 40.9vol% BTnf-Ag82.6, and the dielectric constant of the composite material BTnf/PVDF is 62.4, an increase of 32%. The dielectric loss of the 41.8vol% BTnf-Ag composite is 0.053, and the dielectric loss of the BTnf/PVDF composite is 0.049; the dielectric loss is reduced by 8%. The reason for this phenomenon may be that when the volume fraction reaches 41.8 filling, with the increase in the Ag content of the particles, a filter system is formed inside the composite material, the dielectric constant increases suddenly, and the dielectric loss increases [20]. When creating the sculpture of Nuwa, the tail needs to be made of clay to make scales. In order to show its compassionate and obligatory vibe, we can suspend it in a vacuum at the bottom of the ceramic. The increase in the dielectric constant at this time can undoubtedly drag heavier objects or make them levitate higher. Since the suspension is electromagnetic, it can increase its singularity and divinity. Using the optical properties of ferroelectrics, the tail scales can radiate fluorescence, making it unique and beautiful. If it is an outdoor exhibition of sculptures, it is possible to form a spatial three-dimensional sculpture without connecting objects, supporting it with dielectric properties, bringing the visual shock of the image.


### 3.3. The Energy Storage Behavior of the Btnf-Ag/Pvdf Composite Material and the Influence of Dielectric Properties on Environmental Sculptures

BTnf-Ag/PVDF composite materials not only require excellent dielectric properties, but also good energy storage density. However, high breakdown strength is a necessary condition for high energy storage density, and hence the DC breakdown strength test research of the composite materials is very important [21].As shown in Figure7, according to the linear fitting of the Weibull compound formula, the score of the pure PVDF force matrix can be calculated to be 375 MV/m. When the volume fraction of BTnf-Ag is 2.5vol%, the energy fraction is reduced to 334 MV/m. When the volume fraction of BTnf-Ag is 5vol%, the breakdown force is reduced to 261 MV/m, and when the volume fraction of BTnf-Ag is 7.5vol%, the breakdown force is reduced to 227 MV/m. It reduces the breaking strength by 10vol% to 185 MV/m. The main reason for the decrease in breaking strength is: the presence of Ag particles in the BTnf-Ag hybrid fiber leads to an increase in the probability of contact between them. A more effective network is formed in a local area, and it is easy to break under the action of the electric field. For example, in sculptures, the corresponding electric field can be used to calculate the deformed shape of the model. Separation can be used to ensure that the sculpture is correctly removed from the outside. Based on the content, we can also calculate where it falls. Hand-paintings can form their own sculptures if it is encouraged, and the shape of the sculptures can be enhanced according to the accuracy of how air and rhyme are. In some cases, the external sculpture has been eroded, the surface has been dyed, and the outer layer is muddy, which does not require precise polishing. Only the material requirements must be calculated correctly. According to the anti-pulse power, the electricity will clean itself [22]. Generally, energy density and energy efficiency storage determine the higher performance of dielectric capacitors. The force conservation of logarithmic density (−ln(1 − p)) is the release of capacitor density. The higher the energy density in the attack, the higher the discharge energy density. The larger the capacitance, the greater the load and emission efficiency, and the better the capacitance performance [23]. In practical applications, the preparation of high energy density capacitors with high load and discharge efficiency has become a major problem. Figure 8 shows that when the content of BTnf-Ag increases, the energy density will first increase and then decrease, and the emission efficiency of the load will gradually decrease. The reason is: the composite material with low content has high fracture strength, and the composition of high content material is reduced. The dielectric strength of BTnf-ag plays an important role [24–26]. For example, at 245 MV/m, the energy density and emission efficiency of the nanocomposite containing 5vol% BTnf-Ag are 9.87 J/cm3 and 62.31%, respectively. At 325 MV/m, the energy density and load emission efficiency of pure PVDF are 4.98 J/cm3 and 720.35%, 5vol%BTnf-Ag, respectively. Nanocomposites have higher energy efficiency and higher load and discharge efficiency than other rounded corners.Figure 7
Weibull DC breakdown strength of the BTnf-Ag/PVDF composite.Figure 8
Hysteresis loop, energy storage density, and leakage current of the BTnf-Ag/PVDF composite material.Current density is the current distribution per unit area of a dielectric material under an electric field. Current density is an important parameter to evaluate the electrical insulation of composite materials under an electric field. Current density is important for the design of power systems and electronic systems. The greater the applied electric field, the higher the current density, the higher the breakdown strength, the higher the electrical displacement, and the greater the energy storage density. As the electric field increases, the current density gradually increases. Under the same electric field, as the BTnf-Ag filler increases, the current density also increases slowly. For example, at 100 MV/m, the current density of pure PVDF is 1 × 10−6 A/cm2, and the current density of 5vol%BTnf-Ag composite material is 5 × 10−6 A/cm2. Due to the introduction of nano-Ag particles, the current density has increased several times, but the composite material still maintains excellent insulation properties. By increasing the current density, the sculpture has a better ability to apply electricity when highlighting the light perception. In some necessary occasions, such as outdoor lighting atmosphere, it can create a stronger effect.


## 3.1. Experiment Part

Dissolve the prepared barium-titanium nanofiber fixed power supply in 300 ml of absolute ethanol, and ultrasonically mix for 5 minutes until a uniform and stable white emulsion is obtained. The white emulsion was prepared and precipitated at 800 r/min and transferred to an oven at 70°C for 10 hours. The white powder was used as the raw material for the next experiment. Weigh out the barium titanate wire and silver nitrate according to the ratio of 2.0 g barium titanate and 0.2 g silver nitrate. Add 300 ml of ethylene glycol solution and mix for 30 minutes until the solution becomes a red emulsion after 5 minutes of sonication. The emulsion was transferred to a glass in a three-necked vial, and then transferred to a heating bath mixed with magnetic oil. Carefully arrange the reaction and keep it for 20 minutes when the temperature reaches 130°C. The color of the final solution was brown, indicating the formation of silver nanoparticles. After the reaction was completed, the three-necked balloon was taken out of the oil bath and cooled to room temperature naturally. After discarding the separate emulsion, the bottom layer was centrifuged and mixed, washed with ethanol solution for 3–5 times, and then the precipitate was transferred to a drying box for 24 hours to obtain BTnf. Using a hybrid optical fiber substitute instead of -ag, weigh BTnf-Ag and PVDF powder in a prescribed manner at room temperature, and dissolve PVDF in a certain amount of DMF. Ultrasonic mixing was performed at 40°C for 30 minutes, and the BTnf-Ag powder used for the above-mentioned purposes was spined out. Melt in the mixture and stir in the ultrasonic solution for 15 minutes. The resulting mixture was then coated in a clean glass dish, and then transferred to a drying oven at 70°C for 12 hours. Finally, the composite screen is quickly heated to 180°C. Immediately immerse in ice water, remove from the composite glass screen, and dry at 40°C for 12 hours. We can understand that Ag+ can be reduced to Ag nanoparticles in the solution, and because the silver particles are discretely dispersed on the surface of the titanium-barium fiber, we can understand that the silver nanoparticles are successfully loaded on the surface of the fiber, as shown in Figure5.Figure 5
X-ray photoelectron spectra of BTnf and BTnf-Ag Ag3d3/2.SEM, XRD, XPS, etc., have verified that the silver nanoparticles have been successfully reduced, and the silver nanoparticles are dispersed on the surface of the titanium barium fiber. The change of nano-silver-barium-titanium has a significant effect on improving the polymer interface structure, and it improves the spleen. They are assembled in the distribution of internal materials to reduce the surface porosity of the composite material and prepare alternative materials for testing the dielectric properties of the composite material.


## 3.2. Study on the Dielectric Properties of the Btnf-Ag/Pvdf Composite

We first prepared samples with different component contents according to the fixed ratio of BTnf-Ag and PVDF. We use the formula to calculate the contents of BTnf-Ag(wt), BTnf-Ag(vol), BTnf(vol), and Ag(vo) in the barium-titanium nanofiber sample, as shown in Table2.Table 2
The content of each component in the BTnf-Ag/PVDF hybrid particles.
SampleBTnf-Ag (wt)BTnf-Ag (vol)BTnf (vol)Ag (vol)ɛ/δ (1 kHz)ɛ/δ (100 KHz)PVDF000014.2/0.01513.2/0.057BTnf-Ag/PVDF-124.17.452.421.4/0.01819.9/0.060BTnf-Ag/PVDF-240.214.8104.829.3/0.03027.3/0.059BTnf-Ag/PVDF-360.728.3208.343.3/0.03639.9/0.060BTnf-Ag/PVDF-474.941.83011.882.6/0.04273.8/0.055BTnf-Ag/PVDF-584.355.74015.798.1/0.04989.1/0.049It can be seen from Figure6 that in the range of 1 kHz∼105 Hz, when the content of BTnf-Ag is less than 28.3vol%, the dielectric constant of the BTnf-Ag composite material has a small change, i.e., the dielectric constant. It is a composite material with relatively independent frequency. The main reason is that at relatively low frequencies, the dielectric constant has a weaker relaxation effect on the composite material and has a small contribution to the dielectric constant. At the same time, the dielectric constant at low frequencies is relatively low. The main reason is that the relative content of BTnf-Ag (the dielectric constant of BaTiO3) is much higher than that of the PVDF polymer matrix, which is the dielectric constant [17]. When the content of BTnf-Ag exceeds 27.3vol%, especially when the content reaches 41.8vol%, and the filler increases by a certain amount, the contact probability of the filler surface inside the composite material increases significantly. Moreover, the Ag particles also enhance the interface polarization. The increase in the electrical constant is greater, and the change in the direction of the positive and negative poles at the center of the dipole moment cannot keep up with the change in the direction of the electric field. Another reason is that the dielectric properties of the filler and the matrix are so different that their ability to trap carriers and electrons in the composite is also different. Increasing the content greatly increases the chance of contact between fillers and increases their frequency. With the increase in the dipole moment, it cannot keep up with the rhythm of the electric field change, the polarizability drops sharply, and the dielectric constant drops significantly [18]. The results show that the continuous dielectric constant will decrease with the increase, and the change of the content product is more obvious.Figure 6
Frequency dependence of the dielectric constant and the dielectric loss of PVDF nanocomposites with different contents of BTnf-Ag and BTnf.When the material is low, the impact frequency on the dielectric loss is small. For example, in the range of 1 kHz to 10 kHz, for 7.4vol% of BTnf-Ag, it can be seen that the dielectric loss of the composite material can be reduced from 0.023 to about 0.021. As the content gradually increases, the dielectric loss of the composite material also increases. For example, in the range of 1 kHz to 10 kHz, when the BTnf-Ag content is 14.8vol%, it can be seen that the dielectric loss of the composite material is reduced from 0.061 to about 0.032. But in the range of 10 kHz to 1 MHz, the dielectric loss first increases and then decreases, and peaks appear. The reason may be that the movement of carriers is blocked, the BTnf-Ag dipole orientation releases polarization, and the material orientation does not follow the polarization. The change in the electric field leads to a higher hysteresis. The polarization formation and transformation of the molecular electric field leads to the loss of molecular chains and increases the energy loss [19]. In the range of 106 to 107 Hz, as the electric field changes, the polarization of the medium cannot continue, the current increases, and a wave crest appears. The introduction of Ag nanoparticles can significantly increase the dielectric constant, while the dielectric loss slightly increases. For example, the dielectric constant of the composite material is 40.9vol% BTnf-Ag82.6, and the dielectric constant of the composite material BTnf/PVDF is 62.4, an increase of 32%. The dielectric loss of the 41.8vol% BTnf-Ag composite is 0.053, and the dielectric loss of the BTnf/PVDF composite is 0.049; the dielectric loss is reduced by 8%. The reason for this phenomenon may be that when the volume fraction reaches 41.8 filling, with the increase in the Ag content of the particles, a filter system is formed inside the composite material, the dielectric constant increases suddenly, and the dielectric loss increases [20]. When creating the sculpture of Nuwa, the tail needs to be made of clay to make scales. In order to show its compassionate and obligatory vibe, we can suspend it in a vacuum at the bottom of the ceramic. The increase in the dielectric constant at this time can undoubtedly drag heavier objects or make them levitate higher. Since the suspension is electromagnetic, it can increase its singularity and divinity. Using the optical properties of ferroelectrics, the tail scales can radiate fluorescence, making it unique and beautiful. If it is an outdoor exhibition of sculptures, it is possible to form a spatial three-dimensional sculpture without connecting objects, supporting it with dielectric properties, bringing the visual shock of the image.


## 3.3. The Energy Storage Behavior of the Btnf-Ag/Pvdf Composite Material and the Influence of Dielectric Properties on Environmental Sculptures

BTnf-Ag/PVDF composite materials not only require excellent dielectric properties, but also good energy storage density. However, high breakdown strength is a necessary condition for high energy storage density, and hence the DC breakdown strength test research of the composite materials is very important [21].As shown in Figure7, according to the linear fitting of the Weibull compound formula, the score of the pure PVDF force matrix can be calculated to be 375 MV/m. When the volume fraction of BTnf-Ag is 2.5vol%, the energy fraction is reduced to 334 MV/m. When the volume fraction of BTnf-Ag is 5vol%, the breakdown force is reduced to 261 MV/m, and when the volume fraction of BTnf-Ag is 7.5vol%, the breakdown force is reduced to 227 MV/m. It reduces the breaking strength by 10vol% to 185 MV/m. The main reason for the decrease in breaking strength is: the presence of Ag particles in the BTnf-Ag hybrid fiber leads to an increase in the probability of contact between them. A more effective network is formed in a local area, and it is easy to break under the action of the electric field. For example, in sculptures, the corresponding electric field can be used to calculate the deformed shape of the model. Separation can be used to ensure that the sculpture is correctly removed from the outside. Based on the content, we can also calculate where it falls. Hand-paintings can form their own sculptures if it is encouraged, and the shape of the sculptures can be enhanced according to the accuracy of how air and rhyme are. In some cases, the external sculpture has been eroded, the surface has been dyed, and the outer layer is muddy, which does not require precise polishing. Only the material requirements must be calculated correctly. According to the anti-pulse power, the electricity will clean itself [22]. Generally, energy density and energy efficiency storage determine the higher performance of dielectric capacitors. The force conservation of logarithmic density (−ln(1 − p)) is the release of capacitor density. The higher the energy density in the attack, the higher the discharge energy density. The larger the capacitance, the greater the load and emission efficiency, and the better the capacitance performance [23]. In practical applications, the preparation of high energy density capacitors with high load and discharge efficiency has become a major problem. Figure 8 shows that when the content of BTnf-Ag increases, the energy density will first increase and then decrease, and the emission efficiency of the load will gradually decrease. The reason is: the composite material with low content has high fracture strength, and the composition of high content material is reduced. The dielectric strength of BTnf-ag plays an important role [24–26]. For example, at 245 MV/m, the energy density and emission efficiency of the nanocomposite containing 5vol% BTnf-Ag are 9.87 J/cm3 and 62.31%, respectively. At 325 MV/m, the energy density and load emission efficiency of pure PVDF are 4.98 J/cm3 and 720.35%, 5vol%BTnf-Ag, respectively. Nanocomposites have higher energy efficiency and higher load and discharge efficiency than other rounded corners.Figure 7
Weibull DC breakdown strength of the BTnf-Ag/PVDF composite.Figure 8
Hysteresis loop, energy storage density, and leakage current of the BTnf-Ag/PVDF composite material.Current density is the current distribution per unit area of a dielectric material under an electric field. Current density is an important parameter to evaluate the electrical insulation of composite materials under an electric field. Current density is important for the design of power systems and electronic systems. The greater the applied electric field, the higher the current density, the higher the breakdown strength, the higher the electrical displacement, and the greater the energy storage density. As the electric field increases, the current density gradually increases. Under the same electric field, as the BTnf-Ag filler increases, the current density also increases slowly. For example, at 100 MV/m, the current density of pure PVDF is 1 × 10−6 A/cm2, and the current density of 5vol%BTnf-Ag composite material is 5 × 10−6 A/cm2. Due to the introduction of nano-Ag particles, the current density has increased several times, but the composite material still maintains excellent insulation properties. By increasing the current density, the sculpture has a better ability to apply electricity when highlighting the light perception. In some necessary occasions, such as outdoor lighting atmosphere, it can create a stronger effect.


## 4. Discussion

Compared with the two ancient BTnf/PVDF composite materials, the BTnf-Ag/PVDF composite material has a higher dielectric constant, and the dielectric loss is not too high. For example, 41.8vol% BTnf-Ag composite material. Its dielectric constant is 82.6, but the dielectric constant of BTnf/PVDF composite material is only 62.4, an increase of 32%. The dielectric loss of the 41.8vol% BTnf-Ag composite material is 0.053, and the dielectric loss constant of the BTnf/PVDF composite material is 0.049; the dielectric loss is reduced by 8% year-on-year. By testing the breakdown strength and hysteresis loop of this composite material, the 5vol%BTnf-Ag nanocomposite material has an energy storage density of 9.87 J/cm3 and an electrical conversion efficiency of 62.31%.This article is dedicated to discussing the preparation of ferroelectric ceramic materials from nanoparticles and their application in outdoor environmental sculptures. This article first describes the ferroelectric ceramics and outdoor environmental sculptures, and then explains the method of preparing ferroelectric ceramics from barium titanate nanoparticles. Firstly, the inverse process of pyroelectricity and the influence of electric field strength on the entropy of ferroelectric ceramic materials are explained based on the principle of electric card effect of ferroelectric ceramic materials. In the form of converting electrical energy into thermal energy, based on the thermodynamics of the Maxwell relationship and the thermodynamics of the Landau phenomenological theory, the system’s elasticity, stress, and temperature conditions are calculated and the influence on the preparation is calculated. The electric card effect of ferroelectric ceramics was tested. Next, the preparation of tetragonal phase barium titanate ferroelectric ceramics prepared by hydrothermal nanoparticles is described. Under high temperature and high pressure, following the principle of the hydrothermal reaction, Ba(CH3COO)2 and Ti(C4H9O)4 are used as raw materials to obtain nanoparticle tetragonal BaTiO3. Then, SBT/Cu ferroelectric ceramic composites were prepared by nanoparticle metallurgy. The methods of powder mixing, cold pressing, and sintering are used to increase the strength of the nanoparticles, and the optimal temperature for sintering the composite material is obtained in the plasma discharge mode. Then the preparation and performance of the high dielectric constant BTnf-Ag/PVDF ferroelectric ceramic nanocomposite through experiments, as well as the application research in environmental sculptures is shown. The barium titanate fiber prepared by electrospinning was used to test the performance before and after the addition of silver ions, and it was found that the composite material with two ancient methods BTnf/PVDF was obtained. By comparison, the BTnf-Ag/PVDF composite material has a higher dielectric constant and the dielectric loss is not too high. Through its dielectric properties in outdoor sculptures, electromagnetic waves can be absorbed. Under certain circumstances, it is transformed into heat, mechanical, or electrical energy. It can reduce its reflection effect, and even in certain scenes, it can reach different angles. Some angles can be invisible and shocking, let alone different angles of vision, resulting in the color change of the sculpture. The above experiment can get a 41.8vol% BTnf-Ag composite material, with its dielectric constant as 82.6, but the dielectric constant of the BTnf/PVDF composite material is only 62.4, an increase of 32%. The dielectric loss of the 41.8vol% BTnf-Ag composite material is 0.053, and the dielectric loss constant of the BTnf/PVDF composite material is 0.049; the dielectric loss is reduced by 8% year-on-year. The ferroelectric ceramic composite prepared by adding silver ions has ideal dielectric properties, and its energy storage density is also enhanced.


## 5. Conclusions

To sum up, it can be seen that ceramic materials in outdoor sculptures are worthy of application, and their advantages are outstanding. At the same time, they can provide more inspiration for creators. The most important thing is that the color of the ceramic glaze remain unchanged for thousands of years. As long as outdoor sculptures are not damaged by the external environment and man-made factors, they can remain unchanged for thousands of years. The experiment demonstrates the preparation and performance of high dielectric constant BTnf-Ag/PVDF ferroelectric ceramic nanocomposites and its application in environmental sculptures. It can be seen that the addition of silver ions can make the prepared ferroelectric ceramic composite material have ideal dielectric properties and enhanced energy storage density. It is found that the dielectric constant of the 41.8vol% BTnf-Ag composite ferroelectric ceramic material is 82.6, but the dielectric constant of the BTnf/PVDF composite material is only 62.4, which is an increase of 32%. The dielectric loss of the 41.8vol% BTnf-Ag composite material is 0.053, and the dielectric loss constant of the BTnf/PVDF composite material is 0.049; the dielectric loss is reduced by 8% year-on-year. By testing the breakdown strength and the hysteresis loop of this composite material, the 5vol%BTnf-Ag nanocomposite material has an energy storage density of 9.87 J/cm3 and an electrical conversion efficiency of 62.31%.



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*Source: 4874150-2022-09-16.xml*