Thermal properties and remnant state variables of ferroelectric ceramics switched by both electric field and compressive stress at room temperature

A commercial poled ferroelectric cube specimen is subject to electric field and compressive stress of various magnitudes at the reference temperature 20 °C. After reaching specific states of remnant polarization and remnant strains, temperature of the specimen increases under no external load, measuring changes in polarization and strains. Assuming constant values of thermal properties in the temperature range of interest, we estimated pyroelectric and thermal expansion coefficients for all tested levels of electric and stress fields and plotted them versus remnant state variables at 20, 50, 80, and 110 °C. The distributions of thermal properties fit well into quadratic curves independent of electric and stress fields at each of the four temperatures. One could predict successfully the quadratic fitting curves at high temperatures by using the equations of quadratic fitting curves at reference temperature. Remnant state variables also seem to have close correlation among themselves, independent of the levels of applied electric field or stress.