Size effect on the phase transition in PbTiO3 fine particles

The finite size effect on the phase transition in PbTiO3 fine particles is described. Very small crystals with an average diameter of 14.2 nm were obtained by lowering the calcination temperature to 400 degrees C. Raman scattering measurements of such fine particles were carried out to study the dependence of the phase transition temperature on the particle size. The X-ray diffraction pattern was also measured to study the tetragonality, c/a ratio. The results strongly suggest the presence of a critical size below which the ferroelectric state becomes unstable. The critical size determined by Raman measurements was 10.7 nm.