Microstructure, electrical properties, and degradation behavior of praseodymium oxides-based zinc oxide varistors doped with Y2O3

Abstract

The microstructure, electrical properties, and degradation behavior of Pr-based zinc oxide varistors, which are composed of Zn-Pr-Co-Cr-Y oxides were investigated according to Y₂O₃ additive content in the range 0.5–4.0 mol%. The majority of the Sadded Y₂O₃ were segregated at the multiple ZnO grain junctions and grain boundaries. The average grain size was markedly decreased in the range 27.3–8.6 μm with increasing Y₂O₃ additive content. Y₂O₃ acted as an inhibitor of grain growth. Additions of Y₂O₃ increased the varistor voltage in the range 36.90–686.58 V/mm, increased the nonlinear exponent in the range 3.75–87.42, decreased the leakage current in the range 115.48–0.047μA, increased the barrier height in the range 1.06–2.16 eV, and decreased the donor concentration in the rang 1.87 × 10¹⁸–0.19 × 10¹⁸ cm⁻³. Y₂O₃ acted as an acceptor, as a result of the decrease of donor concentration. All Pr-based ZnO varistors doped with Y₂O₃ exhibited very predominant degradation characteristics, which show a nearly symmetric I-V after the stress. In particular, since 4.0 mol% Y₂O₃-added ZnO varistor has not only very excellent non-ohmicity, but also very stable degradation behavior, it is estimated to be sufficiently used to various application fields.