Novel Ultrahigh-Performance ZnO-Based Varistor Ceramics.

The nonlinear response of a material to an external stimulus is vital in fundamental science and technical applications. The power-law current-voltage relationship of a varistor is one such example. An excellent example of such behavior is the power-law current-voltage relationship exhibited by BiO-doped ZnO varistor ceramics, which are the cornerstone of commercial varistor materials for overvoltage protection. Here, we report on a sustainable, ZnO-based varistor ceramic, without the volatile BiO, that is based on CrO as the varistor former and oxides of Ca, Co, and Sb as the performance enhancers. The material has an ultrahigh α of up to 219, a low of less than 0.2 μA/cm, and a high of up to 925 V/mm, making it superior to state-of-the-art varistor ceramics. The results provide insights into the design of materials with specific characteristics by tailoring states at the grain boundaries. The discovery of this ZnO-CrO-type varistor ceramic represents a major breakthrough in the field of varistors for overvoltage protection and could drastically affect the world market for overvoltage protection.