Evaluation of Dielectric Strength and Breakdown Behavior for Sr-, Nb-Doped PZT Ceramics with Various Shapes of Electrodes

Abstract

Dielectric strength (E_bd) and breakdown behavior were evaluated for Sr-, Nb-doped lead zirconate titanate (PZT) ceramics under both d.c. and a.c. electric fields. Three types of specimens were prepared, i.e., a concave disc (CSD), partially electroded disc (PED) and wholly electroded disc (WED). The E_bd values measured under the d.c. field were 17.8kV/mm, 8.6kV/mm and 6.9kV/mm for the CSD, PED and WED, respectively. Breakdown was triggered by crack generation in the CSD and PED. Surface flashover occurred in the WED. No significant dependence of E_bd on temperature was observed at temperatures below 150°C under the d.c. field. The E_bd values measured under the a.c. field were 5.2kV/mm, 3.9kV/mm and 4.7kV/mm for the CSD, PED and WED, respectively. Thermal breakdown occurred for all specimens prior to breakdown due to crack generation or surface flashover. E_bd increased slightly as the frequency of the applied a.c. field decreased. The E_bd values measured under the d.c. field were slightly higher than those of BaTiO₃ and almost the same as those of BaTiO₃-SrTiO₃. The E_bd values measured under the a.c. field were slightly lower than those of BaTiO₃.