Query: microwave BaTiO3

title: Percolation phenomena of dielectric permittivity of a microwave sintered BaTiO3 Ag nanocomposite for high energy capacitor
abstract: In the present study, the Alkoxide Hydroxide sol gel process is utilized for the synthesis of barium titanate silver (BaTiO3 Ag) nanocomposite in an inert atmosphere. The high value of dielectric constant having less tangent loss is obtained along with increasing conductivity with Ag content. Moreover, by the inclusion of the conductive phase in BaTiO3, the increasing value of dielectric properties with decreasing Curie temperature is investigated. Sintering of composites was done at 1100 degC for 20 min by using microwave sintering, to improve the densification of ceramic nanocomposites in lesser time with uniform grain size. By increasing the silver content, dielectric constant and tangent loss increased until the percolation threshold ~5% Ag) achieved and suppression of formation of conducting path in composite occurred due to adhesion of silver on barium titanate. Also, at Tc in BaTiO3 Ag (3.5% the highest value of dielectric constant (er) ~9 x 104 with tangent loss ~0.06; several times larger than pure BaTiO3) was obtained due to well dispersion of silver particles in BaTiO3 matrix.

title: Enhanced the dielectric relaxation characteristics of BaTiO3 ceramic doped by BiFeO3 and synthesized by the microwave sintering method
abstract: ) BaTiO3 x BiFeO3 (1 x) BT x BFO) (x 0, 0.01, 0.03, 0.06, 0.1) ceramics with 0.15 wt% SiO2 additive were synthesized by microwave sintering (MWS) and conventional sintering (CS) The crystal structure, micromorphology, dielectric relaxation behavior and ferroelectric properties of (1 x) BT x BFO 0.15 wt% SiO2 ceramics were investigated in detail. The results show that a phase structure transforms from a tetragonal phase to a pseudo cubic phase for all samples and MWS method contributes to refine the grain and make the grain size more uniform. Moreover, a transition undergoes gradually from normal ferroelectric to relaxor ferroelectric is observed. The diffuseness coefficient g of (1 x) BT x BFO 0.15 wt% SiO2 ceramics increases with increasing BFO content and sintered by MWS when x 0.06. The maximum diffuseness coefficient (g 1.69) can be obtained at x 0.06 for MWS ceramic. Polarization electric (P E) hysteresis loops are gradually slimmer as x increasing, and a slimmer P E hysteresis loops is obtained by MWS method. The remnant polarization and coercive field reduce using BFO dopant and MWS method, which also suggests that the dielectric relaxation behavior is strengthened. These results indicate that BFO dopant and MWS technique are both effective methods to improve the relaxation behavior of BT based ceramics.

title: Impact of Al2O3, TiO2, ZnO and BaTiO3 on the microwave absorption properties of exfoliated graphite/epoxy composites at X band frequencies
abstract: Bi filler composites composed of exfoliated graphite (EG) and any one of Al2O3, BaTiO3, ZnO and TiO2 metallic oxides are fabricated in epoxy matrix to improve microwave absorption properties exclusively in X band. These composites are characterized for their morphology and compositional studies using SEM, Raman spectroscopy and X rays photoelectron spectroscopy. The strong reflection loss values of 43 dB (99.995% absorption) 25.7 dB (99.731% absorption) 33.9 dB (99.959% absorption) and 46.0 (99.997% absorption) with wide effective bandwidths are successfully achieved by the EG/epoxy composites containing 40 wt% Al2O3, 30 wt% BaTiO3, 30 wt% TiO2 and 20 wt% ZnO when the thicknesses are 1.8, 1.6, 1.4 and 1.8 mm, respectively. These absorption performances are attributed to the perfect matching conditions, multiple internal reflections, interface polarizations and defect polarizations. The incorporation of metallic oxides demonstrated improved adhesion and reinforcement efficiency factors, as well as uplifted the values of flexural strength and thermal conductivity of EG/epoxy composites. These properties justifies the potential future of metallic oxide/EG/epoxy composite in microwave absorption applications.

title: Space confined Synthesis of Core shell BaTiO3@carbon Microspheres as a High performance Binary Dielectric System for Microwave Absorption.
abstract: Binary dielectric composites are appearing as a kind of promising candidate for conventional magnetic materials in the field of microwave absorption. Herein, we demonstrate the successful fabrication of core shell BaTiO3@carbon microspheres through a space confined strategy. The electromagnetic properties of BaTiO3@carbon microspheres can be easily tailored by manipulating the relative content of carbon shells. It is confirmed that dielectric loss of these composites mainly benefits from conductivity loss, dipole orientation polarization, and interfacial polarization, and the core shell configuration shows its positive contribution to the reinforcement of interfacial polarization. When the content of carbon shells is optimized, the as obtained composite will display excellent microwave absorption performance due to decent attenuation and well matched impedance. The strongest reflection loss can reach up to 88.5 dB at 6.9 GHz with the absorber thickness of 3.0 mm, and the qualified bandwidth below 10.0 dB covers 9.0 12.0 GHz when the thickness is designated at 2.0 mm. Such a performance in X band is superior to those of most typical binary dielectric systems. More importantly, these BaTiO3@carbon microspheres maintain good performance after being treated under high temperature and acidic conditions for a long time, manifesting their promising prospect for practical application. It is believed that these results may be helpful for the development of multicomponent dielectric systems as high performance microwave absorbing materials.

title: CoFe2/BaTiO3 Hybrid Nanofibers for Microwave Absorption
abstract: CoFe2/BaTiO3 hybrid nanofibers (CoFe2/BTO HNFs) have been synthesized via a simple single spinneret electrospinning followed by a calcination and hydrogen thermal reduction process for microwave ab.

title: Influence of Eu valence on the optical activity of BaTiO3 decorated with CaF2 synthesized by microwave assisted hydrothermal method.
abstract: Inorganic hybrid materials have promising applications in absorbers and for the photon harvesting of solar irradiation, such as in DSSC photoanodes. Moreover, investigation of the interactions between the photoanode constituent materials is extremely important, since it is known that the properties of the materials are strongly dependent on the nucleation and growth process. Therefore, the purpose of this work was to synthesize a system consisting of a synergic combination of two inorganic hosts, BaTiO3 and CaF2, synthesized together through a microwave assisted hydrothermal method, which allows single phase materials to be obtained after short synthesis times and at low temperatures. The increase in optical activity was investigated after the insertion of Eu ions. From the structural results, it was possible to observe that the method used to obtain the system was efficient, even using temperatures as low as 140 degC and a reaction time of one minute. The optical properties (emission and excitation) were evaluated in the visible and VUV region from 2.5 to 10.5 eV. The XANES Eu Liii edge differences associated with the XEOL results indicate that the synthesis method incorporated Eu3+ in the hosts and the surface of the two compounds, BaTiO3 and CaF2. Therefore, the combination between the Eu3+ activators and the F centers of the host increased the range for photon harvesting, making these systems a promising material for future applications in photoanodes for DSSCs.

title: Investigations on structural and electrical properties of conventional and microwave sintered BaTiO3 and Ba0.98Nd0.02TiO3 ceramics
abstract: In this article, BaTiO3 and Ba0.98Nd0.02TiO3 ceramics were prepared by high temperature conventional solid state reaction, followed by microwave sintering (MS) process separately. A comparative study on structural, morphological and electrical properties has been employed by powder X ray diffraction (PXRD) Raman, scanning electron microscope and dielectric and ferroelectric measurements. PXRD and profile refinement analysis results revealed that tetragonal phase at room temperature. The Raman spectroscopy provided useful information on the presence of tetragonal symmetry. Surface morphology of the MS sample showed dramatic changes from scanning electron micrographs. Dielectric and ferroelectric behavior observed for MS sample.

title: Microstructure and Microwave Absorption Characteristics of BaTiO3 CoFe2O4 Composites
abstract: Magnetic and dielectric phases like CoFe2O4 and BaTiO3 are both intrinsically capable of absorbing electromagnetic waves. The characteristics of the two phases in a composite structure to obtain the combined effect of the existence of phases as composite components have been investigated. Observation of the microstructure of composites with the composition (1 x)BaTiO3 (x)CoFe2O4 has shown the compact structure of composite sample with an increased the mass density with increasing value of x. No changes in lattice constant of each phase in the composite structure. This ensures that no complete or partial substitution between the ions of each phase has occurred. However, the presence of a material phase in the composite structure influenced the crystallite growth behavior of each phase. The mean crystallite size of the two phases tends to increase, but grew with a different rate. The saturation magnetization value of the composite samples is composition dependent. The value of remanent magnetization and coercivity increases with increasing values of x. All composite samples based on the results of data evaluation data taken by a vector network analyzer (VNA) in X band frequency, shows the ability to absorb electromagnetic waves in all X band frequencies. Composite composition determined the peak frequency that gives the maximum reflection loss value. The largest maximum reflection loss value is 40 dB occurring at a frequency of 10.98 GHz from samples with a composition x 0.5. In conclusion, the composite of CoFe2O4/BaTiO3 system composite can be a promising candidate for electromagnetic wave dampers when the composite is properly designed.

title: Microwave properties of epoxy composites with mixed filler carbon nanotubes/BaTiO3
abstract: The microwave properties of composite materials (CMs) based on epoxy resin and mixed filler carbon nanotubes/barium titanate (CNT/BT) at CNT concentrations up to 5 wt% and 34 wt% of BT were investigated. The complex permittivity of epoxy composites was measured in the frequency range 1 67 GHz via vector network analyzer. The CNT/BT/epoxy composite showed the increase of permittivity with the increase of CNT content in CM. The electromagnetic shielding properties of developed CMs were measured using waveguide spectroscopy in the frequency range from 26 to 37.5 GHz. Increasing of CNT content enhances the conductivity, resulting in an increase of the EMR reflection at the interface air composite as well as EMR absorption inside of the composite. The increase of the shields' thickness (up to 2.5 mm) leads to the increase of shielding effectiveness for transmission up to 30 dB for sample with 5% CNT content due to higher EMR absorption inside, while the changes of the reflection index versus frequency depend on CNT content and composite thickness. The reflection loss (RL) of composites was calculated for various thicknesses using the complex permittivity and the obtained results show that composite 2 wt% CNT/BT/epoxy exhibits superior absorptive properties in the frequency range 10 67 GHz. The BT primary role in such CMs (with conductive fillers) is to move the percolation threshold further for conductive filler, increasing its real part of permittivity.

title: Impedance characterization and microwave permittivity of multi walled carbon nanotubes/BaTiO3/epoxy composites
abstract: Polymer composite materials with mixed fillers are widely investigated due to potentially superior properties they provide compared to a composite with a single filler. In this work, the electrical properties of multi walled carbon nanotubes (MWCNT)/BaTiO3/epoxy composites are investigated using impedance measurements, modeling with equivalent circuit model, determining of alternating current conductivity in the range 10 Hz 2 MHz, permittivity measurements at frequencies 1 67 GHz, and temperature dependencies (77 290 K) of direct current conductivity. Measurements were processed to define the influence of filler combination (carbon nanotubes and BaTiO3) on dielectric properties of the epoxy composites. Nyquist diagrams indicate that all investigated composites have extensive conductive clusters. Permittivity increases monotonically with carbon nanotubes content with a steeper increase of the real part at lower frequencies. Alternating current conductivity has been determined to increase significantly at frequencies over 1 GHz. Temperature dependencies of direct current conductivity in the range 77 293 K exhibit a maximum near 180 220 K, which is shifted to the higher temperatures with the increase of carbon nanotubes content. The observed enhanced values of complex permittivity and electrical conductivity of three phase MWCNT/BaTiO3/epoxy composites lead to a comparatively high microwave attenuation constant, which may be tuned by the carbon nanotubes content in the composite. It suggests that these composites might be perspective shielding and absorbing materials used for microwave applications.