Creep in ferroelectrics due to unipolar electrical loading

Measurements of the time-dependent remanent strain and polarisation due to unipolar electric field loading on initially unpoled, polycrystalline PZT-5H are reported. Specimens were loaded under constant electric field for 300 s, while strain and electric displacement were recorded. Strain gauge drift and electrical leakage in each specimen are corrected using measurements on the same specimen in a fully poled (saturated) state. Linear dielectric and piezoelectric moduli are measured as a function of polarisation in a separate test, allowing remanent strain and polarisation to be deduced from the measured strain and electric displacement data. The hypothesis of a power–law relationship between the remanent polarisation rate and electric field is tested. It is found that a power–law relationship with exponent of about 22 agrees well with the measurements. A relationship governing the saturation of polarisation is given.