Pressure-Induced Phase Transition in BaTiO3 Nanocrystals

The crystal structure and electric properties of BaTiO3 nanocrystals are studied by in situ high-pressure synchrotron radiation x-ray powder diffraction. The phase transition takes place not only in the samples of BaTiO3 nanocrystals that are tetragonal phase with grain sizes more than 100 nm, but also in the samples of BaTiO3 nanocrystals that are cubic phase with grain sizes less than 100 nm. The pressures of phase transition are found to increase with decrease of the grain size from about 4 to 10 GPa for crystallites ranging from 200 to 10 nm in radius. The bulk moduli are calculated according to Birch–Murnaghan state equation before and after the phase transition.