Research method and mechanism analysis of a novel high-performance quaternary Zn-Sr-Co-Sb varistor ceramic

In this paper, a novel high-performance bismuth-free ZnO varistor ceramic was developed involving only three doping elements: Sr, Co and Sb. To specifically study the role of each element in improving electrical properties, a stepwise research method was used for this novel ceramic employing the binary system of Zn-Sr, ternary system of Zn-Sr-Co and quaternary system of Zn-Sr-Co-Sb. Consequently, a possible mechanism corresponding to each doping element is proposed in this work. Moreover, excellent comprehensive properties consisting of a high nonlinear coefficient alpha of 74.30, ultra-low leakage current IL of 0.29 mu A cm-2 and low breakdown voltage gradient E1mA of 361.02 V mm-1 are exhibited in the quaternary Zn-Sr-Co-Sb varistor ceramic, which are superior to most advanced ZnO varistors with fewer dopants. This novel quaternary ZnO varistor ceramic without expensive, volatile, deliquescent and toxic dopants exhibits sustainability, environmental friendliness, low cost and high volume development, providing a new perspective for the design of novel high-performance bismuth-free ZnO varistor ceramics. This paper deduced a possible mechanism to reveal the special role of each element and developed novel high-performance bismuth-free ZnO varistors with fewer dopants.