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 %ΔE1mA/cm2=−7.2%, %Δα = −21.9%, and %ΔJL = 13.0% after applying the multi-pulse current of 1800 A.