Effects of packing fraction and bond valence on microwave dielectric properties of A2+B6+O4 (A2+: Ca,Pb, Ba; B6+: Mo,W) ceramics |
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| Authors: | Eung Soo Kim Byung Sam Chun Robert Freer Robert J Cernik |
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| Affiliation: | 1. Department of Materials Engineering, Kyonggi University, 94-6 Yiei-dong, Youngtong-gu, Suwon 443-760, Republic of Korea;2. Materials Science Centre, University of Manchester, Manchester M1 7HS, UK;1. State Key Laboratory Breeding Base of Nonferrous metals and specific Materials Processing, Guangxi universities key laboratory of non-ferrous metal oxide electronic functional materials and devices, College of Material Science and Engineering, Guilin University of Technology, Guilin, 541004, China;2. College of Information Science and Engineering, Guilin University of Technology, Guilin, 541004, China;3. Key laboratory of inorganic nonmetallic crystalline and energy conversion materials, College of Materials and Chemical Engineering, China Three Gorges University, Yichang, 443002, China;1. School of Electronic and Information Engineering, Tianjin University, Tianjin 300072, China;2. Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072, China;1. Guangxi Universities Key Laboratory of Non-ferrous Metal Oxide Electronic Functional Materials and Devices, Guangxi Key Laboratory of Optical and Electronic Materials and Devices, College of Materials Science and Engineering, Guilin University of Technology, Guilin 541004, China;2. College of Science, Guilin University of Technology, Guilin 541004, China;3. College of Materials and Chemical Engineering, Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials, China Three Gorges University, Yichang 443002, China |
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| Abstract: | Microwave dielectric properties of A2+B6+O4 (A2+: Ca, Pb, Ba; B6+: Mo, W) ceramics were investigated as a function of packing fraction and bond valence. For A2+B6+O4 specimens sintered at 800–1100 °C for 3 h, a single phase with a tetragonal scheelite structure was detected, and the theoretical density was higher than 93% throughout the composition. Although the ionic polarizability of Ba2+ ion was larger than that of Ca2+ ion, the dielectric constant (K) of BaB6+O4 showed a smaller value than that of CaB6+O4. These results could be attributed to changes of the packing fraction due to the effective ionic size. The Q·f value was largely dependent on the packing fraction, as well as the percentages of theoretical density. The temperature coefficients of the resonant frequencies (TCFs) of the specimens were affected by the bond valence of oxygen. The specimens of CaMoO4 sintered at 1000 °C for 3 h showed the K of 10.8, Q·f of 76,990 GHz and TCF of ?22.8 ppm/°C, respectively. |
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