Abstract: A new process of preparing non-linear ZnO varistor ceramics was reported. The optimum processing conditions were determined as follows: Zn(NO₃)₂ and NaOH
as the raw material, the concentration of Zn²⁺ to be above 0.5mol·L^-1, pH value of 7.5, calcining temperature of 300℃, sintering temperature of 1200℃; the varistors with non-linear coefficient of 28 were obtained. The
effect of rare earth element La₂O₃ on the electrical properties of the ceramics was discussed to be: doping at low concentration is helpful to enhance
its breakdown voltage; at high concentration its voltage sensitive properties will disappear. The powder was characterized by XRD and TEM, showing the five-additive
powder to be spherical and with a diameter about 40～80 nm.

Key words: ZnO ceramic, sol-gel process, varistor