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Effect of CdO Addition on Microwave Dielectric Properties of BaxSr1-xTiO3 Ceramics
Doaa A. Abdel Aziz1, Wagdy N. Nour1, Aisha E. Reda1, Eglal R. Souya2
1 Ceramic Department, National Research Centre, 12622, Dokki, Cairo, Egypt
2 Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt
received February 13, 2010, received in revised form March 25, 2010, accepted April 11, 2010
Vol. 1, No. 1, Pages 41-50 DOI: 10.4416/JCST2010-00001
Abstract
Ceramic-based barium strontium titanate (BST) solid solutions with the formula BaxSr1-xTiO3 are very important candidates for millimetre-wave applications (e.g. filters and antennas). Several samples with and without CdO were prepared by means of the conventional solid-state route. Five compositions with (0.00 ≤ × ≤ 0.30) sintered at temperatures in the range 1300 - 1500 °C were investigated. Structural X-ray diffraction analysis confirmed their perovskite structure. The morphology of the sintered ceramic bodies was analysed by means of scanning electron microscopy (SEM) and energy-dispersive X-ray (EDAX) microanalysis. The cavity resonance method was used to measure the dielectric properties at microwave (MW) frequency range 40 MHz – 8 GHz. The results revealed that the microwave dielectric characteristics were strongly affected by different Ba/Sr ratios, the cadmium concentration and the microstructure developed. The addition of CdO (0.10, 0.15 and 0.20 mol %) to BaxSr1-xTiO3 ceramic bodies decreased the sintering temperature, with optimum density being obtained at 1400 °C. The best combination of microwave dielectric characteristics was obtained for BST10 ceramic with 0.20 mol % CdO sintered at 1400 °C/2 h, with dielectric constant (εr) = 291, low dielectric loss = 0.0005 and quality factor (Q × ƒ) = 3281 at 1.8 GHz). This can be attributed to its uniform grain morphologies and fine-grained (≤ 0.1 μm) crystalline phases that are round in shape.
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Keywords
microwave, dielectric properties, microstructure, SrO, BaO, TiO2 and CdO
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