Pulse aging behavior of ZnO–Pr6O11–CoO–Cr2O3–Dy2O3 varistor ceramics with sintering time

The aging behavior against a pulse-current in the ZnO–Pr6O11–CoO–Cr2O3–Dy2O3 varistor ceramics was investigated in accordance with sintering time. The varistors sintered for 1 h exhibited the best clamp characteristics; the clamping voltage ratio was in the range of 1.69–1.92 for the lower pulse-current region (5–50 A) and in the range of 2.0–2.98 for the higher pulse-current region (400–1800 A). The best electrical stability against a pulse-current was obtained by the varistor ceramics sintered for 3 h, with image, %Δα = −21.9%, and %ΔJL = 13.0% after applying the multi-pulse current of 1800 A.