Formation of Varistor Characteristics by the Grain-Boundary Penetration of ZnO-PrOx Liquid into ZnO Ceramics |
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Authors: | Sung-Yong Chun Kazuo Shinozaki Nobuyasu Mizutani |
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Affiliation: | Mizutani Laboratory, Department of Inorganic Materials Engineering, Tokyo Institute of Technology,Tokyo 152, Japan |
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Abstract: | Penetration of a liquid (ZnO-PrO x ) into the grain boundaries of sintered, cobalt-doped ZnO pellets resulted in varistors with breakdown voltages per grain boundary in the 1-2 V range and nonlinearity coefficients of 22-37. The varistors were fabricated by spreading a thin layer of Pr6O11 powder paste on the surface of ZnO pellets and heating to various temperatures (1200°-1400°C) and times (0-60 min). Comparing the varistor properties per grain boundary (e.g., threshold voltage, donor concentration, and barrier height) of liquid penetration to those of conventional method indicated the individual grain boundaries were electrically activated when the samples were heat-treated above liquid-phase formation temperature. |
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