Multiaxial response of hard and soft ferroelectrics under stress and electric field

Samples of soft PZT-5H, hard PZT-4D and Barium Titanate were subjected to multi-axial loading in stress and electric field space. The loading paths were: (i) Poling with electric field, followed by repolarizing with electric field at an angle to the original poling direction. (ii) Proportional (simultaneous) loading with electric field and coaxial compressive stress, the proportions of stress and electric field being varied between tests. In case (i) the poled material was cut to produce faces angled to the original poling direction. The measured material responses are reported and initial switching surfaces are calculated based on an offset from linear response in electric displacement. The measurements are used to assess the features required in micromechanical or phenomenological models of switching.