Degradation behavior against surge stress of Zn-Pr-Co-Cr-Y-Er varistor ceramics modified with Er2O3

The degradation behavior against a surge-current in the ZPCCYE (ZnO-Pr6O11-CoO-Cr2O3-Y2O3-Er2O3) varistors was investigated for different amounts of Er2O3. The addition of Er2O3 has a significant effect on nonlinear electrical properties and surge degradation behavior of the ZPCCYE varistors. Increasing amount of Er2O3 improved the clamp characteristics, in which the clamping voltage (K) decreases at a surge-current of 1-40 A. The varistors added with 0.5 mol% Er2O3 exhibited the strongest electrical stability, with the variation rate of the breakdown field of -3.2%, the variation rate of the nonlinear coefficient of -20.9%, and the variation rate of the leakage current of -40.0% after applying 1000 times for a surge-current of 100 A/cm(2). Furthermore, the varistors added with 0.5 mol% Er2O3 exhibited the good surge withstand capability with the variation rate of the breakdown field of -7.9% after applying the surge-current of 400 A. On the contrary, the varistors added with 0.25 mol% were destroyed after applying the surge-current of 400 A and the varistors added with 1.0 mol% were destroyed after applying 55 times for a surge-current of 100 A/cm(2). (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.