Temperature-gradient investigation of phase transitions in ferroelectrics using cooling and heating stage

A cooling and heating stage has been developed to investigate the properties of materials under temperature gradients. We utilized the ferroelectric material BaTiO3 to show the coexistence of cubic and tetragonal crystal structures within a single crystal at the high-temperature and low-temperature sides, respectively, under the temperature gradient around 403 K. Through the Raman mapping and synchrotron X-ray diffraction mapping, we successfully visualized the coexisting crystal structures along with the boundary. Additionally, using Raman mapping, we also visualized the coexistence state of the higher-temperature-tetragonal and lower-temperature-orthorhombic phases. Our developed stage demonstrated its capability as a means to continuously vary the temperature direction in the composition-temperature phase diagram, providing valuable insights into the phase transitions.