FIELD-INDUCED DESTABILISATION OF HARD PZT CERAMICS

The effective internal bias field E(i) within both poled and unpoled hard PZT ceramics was determined as a function of field amplitude, temperature, and frequency by high field AC cycling. It was shown that the apparent value of Ei increased with the amplitude of the applied field, reaching a maximum at a field level of around 2 kV/mm. A slight reduction in Ei was evident at higher field strengths, which was attributed to an increasingly pronounced transient de-ageing effect caused by the measuring field. Field-driven de-ageing studies revealed a gradual reduction in Ei with time, which appeared to follow a logarithmic time law for poled materials. The form of the de-ageing behaviour for unpoled materials followed more closely the exponential relationship reported by previous authors.