Microstructure and electrical properties of Y2O3-doped ZnO-Pr6O11-based varistor ceramics

The microstructure and electrical properties of varistors, which are composed of ZnO-Pr(6)o(11)-CoO-Cr2O3-Y2O3 (ZPCCY)-based ceramics, were investigated in the range of 0.0-4.0 mol% Y2O3. The Y2O3 microstructurally played the role of inhibition in the densification and grain growth. As Y2O3 content is increased, the density was decreased in the range of 5.5-3.7 g/cm(3) and the average ZnO grain size was decreased in the range of 18.6-3.2 mum. The varistors with Y2O3 exhibited a high nonlinear exponent above 30 compared with that without Y2O3- Y2O3 additive significantly improved the nonlinear properties of ZPCCY-based varistors. The varistor with Y2O3 content of 0.5 mol% exhibited the highest nonlinearity, in which a nonlinear exponent is 51.2 and a leakage current is 1.3 muA. The donor concentration and the density of interface states were decreased in the range of 4.19 x 10(18)-0.14 x 10(18)/cm(3) and 5.38 x 10(12) -1.15 x10(12)/cm(2), respectively, with increasing Y2O3 content. (C) 2002 Elsevier Science B.V. All rights reserved.