Investigation into the creeping polarization and strain in PZT-855 under combined mechanical and electrical loadings

Abstract

The time-dependent remnant polarization and remnant strains evolving with time are measured and modeled on initially unpoled ferroceramic PZT-855 under a compressive stress and an electric field. Experiments reveal that the compression stress significantly inhibits the hysteresis loop curves of the electric displacement and the strain since the two hysteresis loop curves against the applied electric field become narrower and narrower as the compression stress becomes larger and larger. Moreover, the compression stress decreases the coercive electric field significantly when compared to that under an applied purely electric field. The variable tendency of the coercive filed in the present case seems like a power-law curve. It is also seen that the compression stress significantly influences the variable features of the remnant polarization and remnant strains against time although the time-dependent feature still remains. In particular, the larger the compression stress is, the smaller the remnant polarization and remnant strains are. For some extreme cases, the remnant strain transfers from a tensile strain to a compressive strain. The power-law formulation proposed by Liu and Huber (J Eur Ceram Soc 29:2799–2806, 2006) is extended to model the present experimental data. However, unlike those under purely electric fields, as the mechanical loading varies from 0 to 100 MPa, the predicted saturation of the remnant polarization appears much earlier than the present experimental data. This limits the application of the power-law model. Further theoretical investigations are needed which will be given in a sequel.