A temperature-dependent study on the polarization-free straining of barium titanate singlecrystals

Abstract

Previous studies by the authors have shown that, when subjected to combined uniaxialstress and electric field at room temperature, a (001)-oriented barium titanate (BaTiO3) single crystal may display incomplete switching characteristics and a severe disproportionof slope gradients at zero electric field for its polarization and strain hysteresis curves. It isproposed that the likely causes for the observed ‘decoupling’ of switching strain andswitching polarization at room temperature are the cooperative operation of multiple90° switching systems, by which ‘polarization-free’ strain changes could be induced, and the presenceof depolarization fields generated from the unshielded boundaries and/or incompatible domainswithin the crystal. In the present study, the evolution of polarization and strain hystereses ofBaTiO3 single crystals under various electromechanical loading combinations are investigated again at55 °C. When compared to the hysteresis measurements at room temperature,the degree of discrepancy between the slope gradients at zero electricfield for the polarization and strain hysteresis curves measured at55 °C is significantly reduced. This is due to the increase in domain wall mobility at a highertemperature, lowering the extent of incomplete switching at maximum electric field. At55 °C, domainswith 180° relative orientation are less likely to exist at maximum electric field; hence, the criticalprerequisite for polarization-free straining is no longer available. The experimental dataobtained in the present study are expected to assist the development of reliable constitutivemodels for single-crystal ferroelectrics.