Influence of Ca-doping on the nonlinear properties of novel ZnO-Cr2O3-based varistor ceramics |
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| Affiliation: | 1. CAS Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 201899, China;2. Department for Nanostructured Materials, Jozef Stefan Institute, Ljubljana, SI-1000, Slovenia;1. Key Laboratory of Green Fabrication and Surface Technology of Advanced Metal Materials (Anhui University of Technology), Ministry of Education, Ma''anshan, 243002, PR China;2. Key Laboratory of Metallurgical Emission Reduction & Resources Recycling (Anhui University of Technology), Ministry of Education, Ma''anshan, 243002, PR China;3. Zhengzhou Research Institute of Mechanical Engineering, Zhengzhou, 450001, PR China;4. National United Engineering Laboratory for Advanced Bearing Tribology, Henan University of Science and Technology, Luoyang, 471023, PR China;1. Center for Nanomaterials, International Advanced Research Center for Powder Metallurgy & New Materials (ARCI), Balapur PO, Hyderabad 500005, A.P., India;2. Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India;1. State Key Laboratory of Control and Simulation of Power System and Generation Equipment, Department of Electrical Engineering, Tsinghua University, Beijing 100084, China;2. Xi’an Thermal Power Research Institute Co., Ltd., Xi’an, Shaanxi 710054, China |
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| Abstract: | The influence of Ca-doping on the microstructure development and electrical characteristics was studied in the novel, ZnO-Cr2O3-based, varistor ceramics with the nominal composition (99.47-x) mol% ZnO + 0.1 mol% Cr2O3 + 0.33 mol% Co3O4 + 0.1 mol% La2O3 + x mol% CaCO3, with x ranging from 0 to 6, sintered at 1200 °C. The results showed that, within the limits of the solid solubility of CaO in ZnO, the addition of CaO greatly enhanced the diffusion processes and hence the grain growth, thus broaden the range of breakdown voltages. Moreover, the Ca-doping simultaneously increases the height of the electrostatic Schottky barrier, resulting in a higher nonlinear coefficient of 40 and a lower leakage current of 2.8 μA/cm2. The results are important for the potential application of these novel ZnO-Cr2O3-based varistors, having different nominal voltages and yet suitable dimensions, in overvoltage protection across a broad range of voltages. |
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| Keywords: | Zinc oxide Varistor ceramics Ca-doping Microstructure Electrical properties |
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