PULSE WITHSTANDABILITY OF THE HIGH-FIELD ZNO VARISTORS

This paper deals with the investigation of the electrical pulse degrad ation of the high-field ZnO varistor fabricated in the traditional way . Its global properties change appreciably, especially the threshold f ield and the nonlinear coefficient. In contrast, the grain boundary ba rrier height remains unchanged despite the decrease in the depletion l ayer thickness after the application of large-current pulses (3 kA upw ard). These observations suggest that the degradation of a high-field ZnO varistor under strong electrical stress is due rather to the degra dation of the thickness of the barrier than to that of its height.