Preparation of Rare Earth Oxide Doped ZnO Varistor and its Electrical Properties

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-l ， 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.