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.