1997 年 105 巻 1220 号 p. 308-311
Dielectric strength (Ebd) 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 Ebd 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 Ebd on temperature was observed at temperatures below 150°C under the d.c. field. The Ebd 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. Ebd increased slightly as the frequency of the applied a.c. field decreased. The Ebd values measured under the d.c. field were slightly higher than those of BaTiO3 and almost the same as those of BaTiO3-SrTiO3. The Ebd values measured under the a.c. field were slightly lower than those of BaTiO3.