Anomalous microwave dielectric behaviour induced by the orthorhombic-tetragonal phase transition in CaLaGaO4 ceramics |
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| Affiliation: | 1. 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. Guangxi Key Laboratory of Optical and Electronic Materials and Devices, College of Material Science and Engineering, Guilin University of Technology, Guilin, 541004, China;1. School of Environmental and Material Engineering, Yantai University, Yantai, 264005, Shandong, China;2. Yantai University, Yantai, 264005, Shandong, China;3. School of Materials Science and Engineering, University of Jinan, Jinan, 250022, Shandong, China;4. State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China;5. SDEE Hitachi High-Voltage Switchgear Co.,Ltd., Jinan, 250000, Shandong, China;1. College of Electronic Information and Engineering, Hangzhou Dianzi University, Hangzhou, China;2. School of Materials Science and Engineering, Zhejiang University, Hangzhou, China;3. College of Materials Science and Engineering, Liaocheng University, Liaocheng, China;1. Guangxi Key Laboratory of Optical and Electronic Materials and Devices,Key Laboratory of New Processing Technology for Nonferrous Metal & Materials", College of Material Science and Engineering, Guilin University of Technology, Guilin, 541004, China;2. College of Materials and Chemical Engineering, China Three Gorges University, Yichang, 443002, China |
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| Abstract: | In this work, orthorhombic (o-) and tetragonal (t-) phase CaLaGaO4 ceramics were synthesized using a conventional solid-state method. Phase evolution and crystal structure were investigated via XRD and TEM, and o-CaLaGaO4 phase with Pna21 space group can be obtained at a low temperature (<1260 °C). With the increase in sintering temperature, o-CaLaGaO4 and t-CaLaGaO4 phases (I4/mmm) coexisted when sintered in the range of 1280 °C – 1300 °C. The microwave dielectric properties of the o-CaLaGaO4 ceramic sintered at 1240 °C were εr = 11.2, Q × f = 63,900 GHz, and τf = ?56.6 ppm/℃. By contrast, the phase transformation in the CaLaGaO4 ceramic led to a significantly increased εr (19.5) in t-CaLaGaO4 and a near-zero τf (+2.3 ppm/℃). The theoretical permittivity (εth) was calculated on the basis of the Clausius–Mossotti equation and P-V-L theory. Results indicate that in the low-symmetry-structure o-CaLaGaO4 ceramics, εth can be estimated accurately by the latter. |
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| Keywords: | Phase transition Microwave dielectric properties P-V-L theory |
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