Meso- to nano-scopic domain structures in high Curie-temperature piezoelectric BiScO3–PbTiO3 single crystals of complex perovskite structure†
Bismuth scandate–lead titanate (BS–PT) solid solution is of great interest as a promising piezoelectric material for high-temperature electromechanical applications due to its excellent comprehensive electric performance and high Curie temperature. However, the full understanding of the ferro-/piezo-electric properties of BS–PT has been strongly hindered by the lack of detailed investigation of microscopic domain structures and successful growth of high-quality crystals. In this work, detailed structural and meso-/nano-scopic domain studies of the BS–PT crystals near the morphotropic phase boundary have been carried out by various characterization techniques. The multi-scale domain structures in the 〈001〉cub-cut 0.324BS–0.676PT single crystals were investigated by a unique combination of temperature-variable birefringence imaging microscopy and piezoresponse force microscopy, in conjunction with high-resolution X-ray diffraction in the temperature range of 30–500 °C. The crystal was found to exhibit tetragonal symmetry on average at room temperature and showed a transformation to cubic symmetry around 460 °C. Complex domain structures with small domain sizes (2–6 μm) and a high density of domain walls were imaged and analyzed from meso- to nano-scopic scale, and more interestingly, local crystal distortion was found in the vicinity of the dense domain walls. The domain evolution as a function of temperature and the correlation between the domain structure and the dielectric properties have been studied. These studies of domains, symmetries and phase transitions provide a better understanding of the structure of BS–PT crystals and other related ferro-/piezo-electric single crystals on multiple length scales, and help design novel high-TC, high performance ferro-/piezo-electric materials.