Tubular channel growth in piezoelectric ceramics under electric fields

Tubular channel growth in a piezoelectric material with a conductive channel is investigated. Breakdown tests are performed on PZT807 samples with cylindrical bar shapes under purely electrical loading. It is experimentally observed that dielectric breakdown occurs via the formation of tubular channels, and the new tubular channel propagates in a straight direction through the specimen. The three-dimensional J integral for a tubular channel is used as a criterion for dielectric breakdown failure. The J integral at the onset of breakdown is calculated numerically through finite element analysis. The critical J integrals at the onset of breakdown are obtained.