WO3 ‐Based Varistor Ceramics of Low Breakdown Voltage

Summary

Electronic and microelectronic systems are eager for the low breakdown voltage varistors. WO₃‐based varistor ceramic is a new kind of low‐voltage varistor with low threshold electric field, small operating current, and high nonlinear coefficient. The high dielectric constant of WO₃‐based varistors enables them to act as a varistor in parallel with a capacitor, which is attractive for applications in the elimination of electrical noise of micromotors, protecting contact of delays, and absorbing discharges of some circuits. Known experimental facts indicate the complication of electrical properties of tungsten oxide, which depends on fabricating conditions and exhibits many phase transitions in a wide temperature range. A double‐Schottky barrier model is introduced to explain the nonlinear behavior of WO₃‐doped ceramics. The polarization caused by phase coexistence destroys the stability of electrical properties of WO₃‐based varistors. It is a great challenge to improve the stability of the physical properties of WO₃ ceramics. Instable electrical properties of WO₃ ceramics can be successfully eliminated by CeO₂ and other rare earth oxide dopings.