Hysteresis behaviors of barium titanate single crystals based on the operation of multiple 90° switching systems

Large strain actuation in barium titanate (BaTiO3) single crystals subjected to combined uniaxial stress and electric field is examined. A maximum strain of about 0.45% is measured under a combined loading of 2.7 MPa compressive stress and ±1.25 MV m−1 cyclic electric field. Above 2.7 MPa, the crystal does not cycle fully between the in-plane and out-of-plane polarized states due to large compressive stress, and consequently, a considerable reduction in actuation strain is apparent. The hysteresis evolution of the crystal under combined electromechanical loading reveals incomplete switching characteristics and a considerable disproportion of slope gradients at zero electric field for the measured polarization and strain hysteresis curves. A likely cause for the disproportion of slope gradients is the cooperative operation of multiple 90° switching systems by which “polarization-free” strain changes are induced. An in situ domain observation study reveals the formation of bubble-like micro-domains prior to the macroscopic 90° switching of the crystal bulk. The presence of these bubble-like “switching weak points” indicates that regions within the BaTiO3 single crystal do not necessarily switch 90° at the same time, and hence, in a way, supports the existence of multiple 90° switching systems. Results obtained in the present study are expected to assist the development of reliable constitutive models for single crystal ferroelectrics.