Microstructure and Electrical Properties of ZPCCYT Varistor Ceramics

The Microstructure and nonlinear electrical properties of the ZPCCYT (ZnO-Pr6O11-CoO-Cr2O3-Y2O3-Tb4O7) varistorswere investigated for different amounts of Tb4O7. The addition of Tb4O7 has a significant effect on microstructureand electrical properties. Analysis of the microstructure indicated that the ceramics consisted of ZnO grain as a mainphase and a few secondary phases as a mix of Pr6O11, Y2O3, and Tb4O7. As the amount of Tb4O7 increased, the sintereddensities of pellets increased from ρ = 5.70 to 5.78 g/cm3 and the average grain size decreased from d = 4.8 to 3.6 μm.The increase in the amount of Tb4O7 increased from EB = 7,473 to 10,035 V/cm and from α = 39.7 to 52.2. In particular,it was found that the ceramics modified with 1.0 mol% in the amount of Tb4O7 are suited for the varistors for highvoltage in the light of a high sintered density and a high voltage gradient.