Electrical properties and aging characteristics of terbium-doped ZPCC-based varistors

The microstructure, electric field-current density (E-J), capacitance-voltage (C-V), and aging characteristics of Zn-Pr-Co-Cr oxide (ZPCC)-based varistors were investigated for different Tb4O7 amounts. It increased in the range of 8.9-42.0 in the non-linear coefficient and in the range of 1026-6514 V cm−1 in the breakdown field with increasing Tb4O7 amount. As Tb4O7 amount increased, the donor density decreased in the range of 1.23-0.70 × 1018 cm−3, whereas the barrier height at grain boundaries increased in the range of 0.73-0.93 eV. A good stability was obtained in the range of 0.25-0.5 mol% in Tb4O7 amount.