Grain size effect on ferroelectric phase transition in Pb1 − xBaxTiO3 ceramics

Abstract

Micro-Raman scattering measurements in the frequency range of 5–1000 cm −1 as well as X-ray diffraction have been carried out on nanocrystalline Pb 1 − x Ba x TiO 3 system. A grain size and Ba ion-induced phase transition from the tetragonal ferroelectric phase of PbTiO 3 to the cubic paraelectric phase of BaTiO 3 is found to occur at x~0.7 and it is associated with the “softening” of the mode at 74 cm −1 ( x = O) which arises from a delicate balance between long-range Coulomb forces and short-range repulsion. A lowest frequency phonon mode at 10 cm −1 is detected and its grain size, Ba composition and temperature dependence appears to be correlated with structures for ABO 3 oxides. The temperature dependence of Raman phonon modes for Pb 0.66Ba 0.4TiO 3 with grain size of 60 nm reveals a temperature-induced soft mode phase transition occurring at 360K.