537 / 2022-03-29 10:55:23

Study on the Microstructure and Electrical Properties of WO3-based Varistor Ceramics by Cold Sintering Process

CSP, WO3-based ceramics, electrical properties, capacitor-varistor

WO₃-based varistor ceramics exhibit good non-linear electrical properties characterized by low voltages and small currents, which are expected to be widely used in the field of microelectronics. Nonetheless, it has always been a challenge to prepare dense varistor ceramics with grain sizes of nano/submicron using conventional high temperature sintering processes. Here, the microstructure, non-linear electrical properties, and dielectric properties of NiO-doped WO₃ ceramics prepared by cold sintering process (CSP) at 300 °C are investigated. The results show that the novel CSP is capable of successfully preparing high-density WO₃-based varistor ceramics. The presence of a second phase NiWO₄ between the grains of WO₃-based varistor ceramics inhibits grain growth. A small quantity of NiO can significantly improve nonlinear properties of the WO₃ ceramics. WO₃-based varistor ceramics with 1 mol% NiO exhibit improved non-linear electrical properties with a low breakdown voltage of 11 V/mm and a large nonlinear coefficient of 16. The non-linear electrical behavior of NiO-doped WO₃-based varistor ceramics can be attributed to the grain boundary interface defects. Additionally, the dielectric permittivity of NiO-doped WO₃ ceramics is significantly enhanced, which enables it working as a capacitor-varistor materials.