Structural and electrical properties of ZnO-V2O5-TiO2-Co2O3-MnO varistor ceramics with low sintering temperature

With the rapid development of electronic components toward miniaturization and integration, ZnO-based varistor ceramics sintered at a low temperature below 961 degrees C have received extensive attention. This work systematically explored the effect of sintering temperature on the microstructure and electrical properties of 98 mol%ZnO + 0.5 mol%V2O5 + 0.5 mol%TiO2 + 0.5 mol%Co2O3 + 0.5 mol%MnO (short for ZVTCM) ceramics prepared via a conventional solid-state method. The X-ray diffraction results revealed that all the ZVTCM ceramics consist of major ZnO grains, and minor secondary phases, including Zn-3(VO4)(2) and Mn2TiO4. Furthermore, the average grain size was found to increase from 2.69 to 11.42 mu m until the sintering temperature reaches up to 925 degrees C. Higher sintering temperature results in an abnormal grain growth behavior and increased content of oxygen vacancies in ZVTCM ceramics, tending to degrade the varistor properties. Excellent varistor properties can be available in the ZVTCM ceramic sintered at 850 degrees C, involving a nonlinear coefficient (alpha) of 21.9, a leakage current density (J(L)) of 59.4 mu A/cm(2), and a breakdown electric field (E-1mA) of 523 V/mm.