Pressure-Driven Depolarization in BaTiO₃ and BaTiO₃-Based Solid Solutions and Stability of Polar Nanodomains in BaTiO₃

The pressure-dependent polarization of single-crystal and polycrystalline BaTiO3 and of BaTiO3-based solid solutions, was studied using second harmonic generation (SHG) to probe polarization directly. In single-crystal BaTiO3, the SHG intensity persisted above the Curie pressure, with remaining intensity attributed to polar nanoregions. Based on these findings, the pressure–temperature phase diagram of BaTiO3 was extended to include a stability field for polar nanodomains above the Curie point. In polycrystalline BaTiO3 and related solid solutions, a positive correlation between Curie pressure and temperature was observed. Complementary DFT calculations confirmed a pressure-induced reduction in SHG activity, linked to the symmetrization of the position of Ti in the structure.