Phase coexistence evolution of nano BaTiO3 as function of particle sizes and temperatures

Using high resolution synchrotron x-ray diffraction, we systemically study the crystal structure evolution of nano BaTiO3 as function of temperatures and particle sizes. In the temperature range from 200 K to 450 K, the nano BaTiO3 with different particles in the range from 5 nm to 100 nm are phase coexisting. The phase fraction evolutions of different nano BaTiO3 indicated that there is an anomaly at particle size around 20 nm, a phase reentrance taking place. The competition of the shear stresses and the compressive stresses on the particle surface, and the delicate balance between them are responsible for the reentrance phenomenon.