Microstructure, electrical properties, and degradation behavior of praseodymium oxides-based zinc oxide varistors doped with Y_(2)O_(3)

摘要

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 Y_(2)O_(3) additive content in the range of 0.5-4.0 mol%. The majority of the added Y_(2)O_(3) were segregated at the multiple ZnO grain junctions and grain boundaries. The average grain size was markedly decreased in the range of 27.3-8.6 μm with increasing Y_(2)O_(3) additive content. Y_(2)O_(3) acted as an inhibitor of grain growth. Additions of Y_(2)O_(3) increased the varistor voltage in the range of 36.90-686.58 V/mm, increased the nonlinear exponent in the range of 3.75-87.42, decreased the leakage current in the range of 115.48-0.047 μA, increased the barrier height in the range of 1.06-2.16 eV, and decreased the donor concentration in the range of 1.87×10~(18)-0.19×10~(18) cm~(-3). Y_(2)O_(3) acted as an acceptor, as a result of the decrease of donor concentration. All Pr-based ZnO varistors doped with Y_(2)O_(3) exhibited very predominant degradation characteristics, which show nearly symmetric I-V characteristics after the stress. In particular, since 4.0 mol% Y_(2)O_(3)-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.