Influence of Sintering Temperature on the Electrical Properties of (La, Ta)-Doped TiO_2 Capacitor-Varistor Ceramics

摘要

An investigation was made of low voltage TiO_2 varistors doped withTa_2O_5 and La_2O_3. TiO_2 ceramics doped with 0.7 mol% La_2O_3 and 0.1 mol% Ta_2O_5 were sintered at different temperature ranging from 1350 to 1450 °C. The influence of sintering temperature on microstructure and nonlinear properties of the (La, Ta)-doped TiO_2 ceramics was studied. The varistor of 99.2 mol%-0.7 mol%La_2O_3-0.1 mol% Ta_2O_5 composite sintered at 1380 °C has a maximal nonlinear coefficient of α =5.2 and a low breakdown voltage of 7.6 V/mm, which is consistent with its highest grain-boundary barriers. According to these results, it is suggested that the sample sintered at 1380 °C forms the most efficient boundary barrier layer. Therefore, the sintering temperature is a very important varible which should not be despised in the project of TiO_2 based varistors production.