L. KE (State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, P. R. China) D. M. JIANG (State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, P. R. China) X. M. MA () (State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, P. R. China)
Abstract
The electrical and microstructural properties of a series of ZnO-based thick film varistors (TFVs) doped with 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10 mol% Y2O3 were studied. It was found that sample doped with 0.08 mol% Y2O3 showed the highest potential gradient of 3159.4 V/mm with a leakage current of 36.4 μA and a nonlinear exponent of 13.1. The ZnO grain size decreased with increasing Y2O3 content, which was the origin for the increase in potential gradient. Raman spectra results showed that the tensile stress increased linearly with Y2O3 doping. Larger tensile stress was considered to result from the lattice distortion and inevitably influenced the grain boundary characteristics. While the Y2O3 doping concentration was beyond 0.08 mol%, the effect of residual stress on electrical properties was much more remarkable than that of grain size, leading potential gradient to be weakened. As a result, high potential gradient of ZnO-based TFVs could be obtained with Y2O3 doping concentration of 0.08 mol% and qualified as excellent candidates for high voltage varistor application.
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Article provided by World Scientific Publishing Co. Pte. Ltd. in its journal Surface Review and Letters.