LOW-TEMPERATURE SINTERING OF ZnO-Bi₂O₃-BASED VARISTOR CERAMICS FOR ENHANCED MICROSTRUCTURE DEVELOPMENT AND CURRENT-VOLTAGE CHARACTERISTICS

O 3 -based varistor ceramics are typically sintered at temperatures above 1100C to ensure the proper microstructure development and the required current-voltage (I-U) characteristics. In this investigation the influence of the sintering regime at temperatures between 800 and 950C on the microstructure development and the I-U characteristics of varistor ceramics was studied. It was shown that the presence of a sufficient amount of Bi 2 O 3 -based liquid phase at the proper Sb 2 O 3 -to-Bi 2 O 3 ratio enhanced the sintering and also promoted grain growth under the influence of the inversion boundaries (IBs) triggered in the ZnO grains by the Sb 2 O 3 . The well-developed microstructures with high density and grain sizes from 4 to 8 m resulted in good current-voltage characteristics of the samples with a coefficient of nonlinearity equal to about 30 and a low leakage current I L of below 1 A. Depending on the composition and the sintering regime, the threshold voltages V T were in the applicable range from 270 Vmm -1 to 850 Vmm -1 , even though values much greater than 1000 Vmm -1 are typically obtained with such low sintering temperatures. * sample were placed directly into furnace heated to temperature T 1 ** cooling rate to room temperature Ceramics -Silikty 62 (1) 8-14 (2018)