# Structural and Dielectric Properties of CuO, PbO and Bi2O3 Doped SrTiO3 Ceramics

T Sofi Sarmash, V Narasimha Reddy, T Vidya Sagar, M Maddaiah, T Subbarao

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T Sofi Sarmash, V Narasimha Reddy, T Vidya Sagar, M Maddaiah, T Subbarao. Structural and Dielectric Properties of CuO, PbO and Bi2O3 Doped SrTiO3 Ceramics. Mechanics, Materials Science & Engineering MMSE Journal. Open Access, 2017, 9, 10.2412/mmse.78.43.129. hal-01504695

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Distributed under a Creative Commons Attribution 4.0 International License
Structural and Dielectric Properties of CuO, PbO and Bi₂O₃ Doped SrTiO₃
Ceramics

T. Sofi Sarmash¹, V. Narasimha Reddy¹,ᵃ, T. Vidya Sagar¹, M. Maddaiah¹, T. Subbarao¹

1 – Materials Science Lab, Dept. of Physics, S K University, Ananthapuramu – 515 003, A. P, India

a – [venkateswararaoikp@gmail.com](mailto:venkateswararaoikp@gmail.com)

<figure><img src="image_2.png" /></figure>

DOI 10.2412/mmse.78.43.129 provided by [Seo4U.link](http://Seo4U.link)

**Keywords:** dielectric properties, glass ceramics, X-ray diffract meter, Ceramic titanates.

**ABSTRACT.** Copper oxide, lead oxide and bismuth oxide each 10% doped separately with 90% SrTiO₃ (ST) ceramic powders were processed by solid-state route technique. We reported the effect of Cu⁺², Pb⁺² and Bi³⁺ ions on the dielectric response of ST and copper addition established the substantial increase in dielectric constant (εᵣ) than undoped ST from 303K-673K and low loss (tanδ) for good dielectric applications. In case of lead doped ST the strong relaxation dynamics of loss factor was observed at higher temperatures and dielectric constant plots established the curie transition temperature T_c = 653K revealing the structural transformation from cubic to tetragonal phase. But bismuth doped ST contrary to the expectations exhibited the decreasing trend of permittivity form 303K-525K and afterwards showed increasing nature with relaxations. The microstructure was examined by field emission scanning electron microscope (FESEM). Some additional phases SrCu₃Ti₄O₁₂, PbTi₃O₇, SrBi₃Ti₅O₁₈ and TiO₂ rutiles were detected by X-ray diffraction technique.

**Introduction.** Copper (II) oxide is a p-type semiconductor of band gap 1.2 eV used to produce dry cell batteries [1]. It can have applications as ceramic resistors, magnetic storage media, gas sensors, semiconductors and solar energy transformation. When transition metals are added up to the ST magnetic as well as ferroelectric properties can be induced. For instance in recent investigations Mn⁺² ions could induce the electric and magnetic dipoles into the system. Likewise as in ref [2, 3] if Cu⁺² ions occupy the Sr⁺² site, dielectric and magnetic anomalies could be induced as the ionic radius of Sr⁺² (0.144nm) is larger than Cu⁺² (0.121nm). But on the other hand anti ferromagnetic spin ordering is being evolved, if Cu⁺² ions occupy the Ti⁺⁴ sites. Even for the higher frequencies copper doped ST showed high dielectric constant. PbO is a toxic material and when doped to strontium titanate (ST) is found experimentally to be a glass ceramic material [4]. Glass ceramics have been commercially used at wide range and limited work has been done over the borosilicate glass ceramic system, in spite of its wide range of applications. The ferroelectric PST thin films have been termed as the candidate materials for the applications in various tunable microwave devices and in high density dynamic random access memories. On the other hand ferroelectric thin films have got much attention in manufacturing various functional devices for optical applications. No detailed report is available in the literature about the dielectric properties of PST ceramics. Both of the materials promote liquid phase sintering at low concentrations about 1-2 % only. Recently in case of bismuth oxide doped ST a novel microstructure was observed which is useful in understanding the grain boundary barrier layer capacitors (GBBLC) and efficient ferro-electric relaxations have been observed for the industrial applications when Bi₂O₃ doped with Ba₀.₈Sr₀.₂TiO₃ ceramics [5]. Yu Zhi et al [6] reported the low temperature and high temperature dielectric properties. In the recent literature Naidu et al. [2-4, 7, 8], Kumar et al. [9] and Maddaiah et al. [2, 10] investigated the effect of various elements (La, Mg, Mn, Cu, Zn & Bi) on electrical properties such as dielectric constant, loss, thermoelectric power, ac-conductivity and dc-conductivity of SrTiO₃ electro ceramic material. In this study the author is
intended to make a novel comparative study of the structural, micro structural and dielectric properties of CuO, PbO and Bi₂O₃ doped ST Ceramics to decrease the sintering temperature of strontium titanate which have not been discussed in earlier literature.

## Experimental Procedure

The ceramic samples of CuO, PbO and Bi₂O₃ 10% each doped individually with 90% SrTiO₃ were prepared by solid state diffusion method. At the outset ST powders have been synthesized using the raw materials of SrCO₃ (99.9% purity) and TiO₂ (99.9% purity). The mixed powders were calcined at temperature 1400°C for 13hrs and the shrinkage of compound was apparently identified. Latter ST was mixed separately with CuO, PbO and Bi₂O₃ and ball milled for nearly 12 hrs. After wards these samples were calcined at 1050°C, 950°C and 1100°C respectively each for 13hrs and the pellets of thickness 0.14cm and radius of 0.62cm have been prepared. The powders and the pellets sintered at 1100°C, 1000°C and 1200°C respectively for 4hrs were characterized using XRD (BRUKER X-Ray Powder Diffract Meter, CuKα) at room temperature and HIOKI 3532-50 LCR HiTESTER (Japan) for structural, surface morphological analysis and dielectric properties respectively. LCR controller over the temperature range from RT to 600°C operated at the frequencies from 42 Hz-5MHz having the heating rate of 0.5°C/min used for dielectric properties.

## Results and Discussions

In fig.1, we reported the comparison XRD spectra of pure and doped ST. Diffraction maxima were observed in the diffraction spectra which are corresponding to the cubic perovskite lattice of ST. The effect of copper ions on the lattice parameter of undoped ST was clearly observed in ref [2] at low concentrations i.e. at low concentration of copper addition to pure ST decreases the lattice parameter (a). Similar reports were achieved in the present investigation. The lattice parameter of pure ST was reported in ref [2] and in case of CuO (10%) doped ST (90%) 'a' value was slightly decreased to 0.3893nm. Since the ionic radius of Cu⁺² (0.121nm) is smaller than that of Sr⁺² (0.144nm) [2]. Along with single perovskite phases some non-perovskite second phases have been detected that correspond to TiO₂ rutiles and SrCu₃Ti₄O₁₂ phases specified in fig.1. Furthermore the average crystalline size (Dₚ=114.9nm) using Scherer formula and average dislocation density (ρ=8.03x10¹³(m⁻²)) were established according to the following equations [11-14].

$$D_p = \frac{k\lambda}{\beta \cos\theta} \rho = D^{-2}$$

where k is a constant and is equal to 0.9, θ is diffraction angle, λ=0.154056 nm (CuKα) and β is full width half maxima.

In the XRD pattern of undoped ST and PbO doped ST (referred as PST in fig.1), it can be seen that the two compounds exhibit cubic crystalline structure having single perovskite reflection peaks with the exception of few additional phases corresponding to the presence of PbTi₃O₇ (PT) and TiO₂ (R) phases [15]. The huge enhancement in the intensity of diffraction lines depends on structure factor (F). At 2-theta angle 32.49° the maximum counts 9730 and similar miller indices (h k l) were noticed as (100), (110), (111), (200), (210), (211), (220) and (310) that of undoped ST. However, the lattice parameters were achieved as a=b=c=3.8930Å and α= β= γ=90° and are in good consistent with literature data. Hence it is confirmed that the structure of present compound is cubic. Depends on obtained lattice parameters the practical value of unit cell volume (59.02x10⁻²⁴cm³) was calculated which is comparable to the unit cell volume of undoped ST as reported in JCPDC file 35-734. Furthermore the average crystalline size (Dₚ=117.2nm). In XRD pattern of bismuth doped ST all peaks are in consistent with the cubic primary phases and Sr₂Bi₄Ti₅O₁₈ was detected as a secondary peak. The lattice constant was found as a=b=c=0.3895 nm.
<table><caption>Table 1. Shows the XRD profile data of CuO doped SrTiO₃ ceramics.</caption><thead><tr><th rowspan="2">2θ</th><th colspan="3">d-space (Å<sup>0</sup>)</th><th colspan="3">D<sub>p</sub>(nm)</th><th colspan="3">px10<sup>-13</sup>(m<sup>-2</sup>)</th></tr><tr><th>CuST</th><th>PbST</th><th>BiST</th><th>CuST</th><th>PbST</th><th>BiST</th><th>CuST</th><th>PbST</th><th>BiST</th></tr></thead><tbody><tr><td>22.842</td><td>3.8930</td><td>3.8930</td><td>3.8831</td><td>110.1</td><td>56.9</td><td>106.5</td><td>8.25</td><td>30.89</td><td>8.82</td></tr><tr><td>32.492</td><td>2.7550</td><td>2.7550</td><td>2.7178</td><td>131.8</td><td>112.5</td><td>117.5</td><td>5.76</td><td>7.9</td><td>8.81</td></tr><tr><td>40.049</td><td>2.2506</td><td>2.2506</td><td>2.2485</td><td>129.8</td><td>130.7</td><td>114.3</td><td>5.94</td><td>5.85</td><td>7.63</td></tr><tr><td>46.56</td><td>1.9498</td><td>1.9498</td><td>1.9482</td><td>123.1</td><td>110.8</td><td>106.0</td><td>6.59</td><td>8.15</td><td>8.9</td></tr><tr><td>52.439</td><td>1.7441</td><td>1.7441</td><td>1.7435</td><td>86.9</td><td>34.4</td><td>70.7</td><td>13.24</td><td>84.5</td><td>20.01</td></tr><tr><td>57.865</td><td>1.5928</td><td>1.5928</td><td>1.5918</td><td>112.6</td><td>108.8</td><td>97.3</td><td>7.89</td><td>8.45</td><td>10.56</td></tr><tr><td>67.908</td><td>1.3795</td><td>1.3795</td><td>1.3792</td><td>113.3</td><td>108.1</td><td>87.6</td><td>7.79</td><td>8.4</td><td>13.03</td></tr><tr><td>77.26</td><td>1.2342</td><td>1.2342</td><td>1.2339</td><td>106.3</td><td>88.4</td><td>79.0</td><td>8.85</td><td>12.8</td><td>16.02</td></tr></tbody></table>

<figure><img src="image_3.png" /><figcaption>Fig. 1. XRD Spectrum of pure, CuO, PbO and Bi₂O₃ doped SrTiO₃ ceramics.</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>Fig. 2. FESEM micrographs of CuO, PbO and Bi₂O₃ doped SrTiO₃ ceramics.</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Fig. 3. Dielectric constant Vs temperature plots of (a) CuO, (b) PbO and (c) Bi₂O₃ doped SrTiO₃ ceramics.</figcaption></figure>

In case of copper doped ST permittivity and loss were decreasing with increase of frequency. These trends were approximately identical in case of undoped ST. At RT sample showed $ε_r$ value of 802 which is almost four times the $ε_r$ value of pure ST and low loss of 0.0046 at RT. In case of lead doped ST initially the permittivity ($ε_r$) is increasing gradually with increase of temperature up to $T_c$ and later showing decreasing trend. Obviously, cubic to tetragonal structural transformation at the Curie-temperature of $T_c$= 653K has been observed. This explicitly established a fact that addition of lead
oxide diminishes the Curie temperature of pure ST. Moreover, the lead addition cannot induce permittivity of pure ST at room temperature. The loss factors (tanδ) were noted as 0.00815 and 0.24837 at 0.1 kHz and 5 MHz respectively (at RT). But for the similar frequencies at 693K tanδ values were obtained sequentially as 1.9544 and 0.07543. Apparently, bismuth doped ST was unable to induce permittivity but showed loss of 0.00935 at RT. Due to the high dielectric constant and low loss established at RT, copper doped ST has got recognition as a candidate material for the applications in electronic devices such as phase shifters, oscillators, micro wave tunable circuits, resonators and charge stored capacitors [16-18].

<figure><img src="image_6.png" /><figcaption>Fig. 4. Dielectric loss Vs temperature plots of (a) CuO, (b) PbO and (c) Bi₂O₃ doped SrTiO₃ ceramics.</figcaption></figure>

**Summary.** In conclusion of this work (i) some additional phases SrCu₃Ti₄O₁₂, PbTi₃O₇, SrBi₃Ti₅O₁₈ and TiO₂ rutiles were detected (ii) in this study low loss was obtained for all ST based dopants for device applications. Especially, copper doped ST induced the permittivity of pure ST.

**References**

[1] "Cupric Oxide Data Sheet". Hummel Croton Inc. 2006-04-21. Retrieved 2007-02-01.

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Cite the paper

T. Sofi Sarmash, V. Narasimha Reddy, T. Vidya Sagar, M. Maddaiah, T. Subbarao (2017). *Structural and Dielectric Properties of CuO, PbO and Bi2O3 Doped SrTiO3 Ceramics*. Mechanics, Materials Science & Engineering, Vol 9. DOI 10.2412/mmse.78.43.129