AC ageing characteristics of Y2O3-doped ZnO varistors with high voltage gradient

In this paper, AC ageing characteristics of high voltage gradient ZnO varistors doped with different Y2O3 concentration were investigated. The voltage gradient of these samples is markedly improved by increasing Y2O3 content, however, the nonlinear coefficient decreases and the leakage current increases at the same time. Y2O3-doped ZnO samples exhibit lower stability under accelerated AC ageing stress of 0.85 V-1mA/135 degrees C/168 h, compared with samples without Y2O3. Double-Schottky barrier(DSB) parameters before and after ageing tests indicate that the decrease of barrier height for traditional sample is less than that for high voltage gradient sample, which should be ascribed to its slight variation in the interface state density. (C) 2011 Elsevier B.V. All rights reserved.