ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 65, (1) 1 - 8 (2021)

Kang Kunyong 1,2,3, Zhu Gang 1,2,3, Chai Xijuan 1,2,3, Deng Shuduan 1,2, 3, Xu Kaimeng 1 ,2, 3
1 Yunnan Key Laboratory of Wood Adhesive and Glued Product, Southwest Forestry University, Kunming 650224, PR China
2 Functional and Wood-based Ceramics Laboratory, Southwest Forestry University, Kunming 650224, PR China
3 School of Materials Science and Engineering, Southwest Forestry University, Kunming 650224, PR China

Keywords: Titanium oxide (TiO₂), Varistor ceramis, Nonlinear coefficient, Breakdown voltage, Hot Isostatic Pressing (HIP) , Post-Annealing

TiO₂-Ta₂O₅-CaCO₃ varistor ceramics were prepared by hot isostatic pressing (HIP) and annealed in oxygen and nitrogen, respectively. The nonlinear coefficient α, the breakdown voltage EB and the leakage current JL of samples were tested using a varistor dc parameter meter. The average barrier height ΦB of the unannealed samples and the samples annealed in oxygen and nitrogen was calculated. The microstructure of samples was analyzed by STEM-EDS, XRD and SEM. TiO₂-Ta₂O₅-CaCO₃ varistor ceramics with uniform microstructure, fine grains and low porosity was obtained by HIP. By annealing, α increases, while EB and JL decrease. When annealing is performed in oxygen, the oxygen enrichment at the grain boundaries is also helpful to increase α and reduce JL. TiO₂-Ta₂O₅-CaCO₃ varistor ceramics with Ta₂O₅ and CaCO₃ contents of 0.20mol% sintered at 1200°C and annealed at 700°C for 3h in oxygen possesses best varistor performance with α =11.2, EB =22.6V·mm--1- and JL =8.7μA·cm-2-.

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doi: 10.13168/cs.2020.0036
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