Microstructure and electrical properties of Dy2O3-doped ZnO–Bi2O3 based varistor ceramics

• ZnO–Bi2O3 based varistor ceramics were prepared by the conventional solid-state route.
• Doping proper amount of Dy2O3 markedly improves the electrical properties.
• Excess sintering temperature deteriorates the electrical properties.

The Dy2O3-doped ZnO–Bi2O3 based varistor ceramics were prepared by a solid state reaction route, and the microstructure and electrical properties were also investigated. The results show that a multiphase composition exists in all samples. With increasing content of Dy2O3, the average size of ZnO grains decreases and the threshold voltage greatly increases. The nonlinear coefficient of the ceramics is in the range of 4.7–60.2, the threshold voltage is in the range of 364.6–884 V/mm, and the leakage current is between 1.77 μA/cm2 and 159.1 μA/cm2. Typically, the varistor ceramics with 0.60 mol.% Dy2O3 sintered at 1050 °C exhibit excellent electrical properties with the threshold voltage of 872.5 V/mm, the nonlinear coefficient of 60.2 and the leakage current of 5.46 μA/cm2. The results show doping Dy2O3 is a promising route for the production of the higher threshold voltage of ZnO–Bi2O3 based varistor ceramics.

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