A study of disorder effects at ferroelectric phase transition in BaTiO3

Abstract The total structure factor of BaTiO 3 obtained by neutron powder diffraction in the temperature range 360–430 K in the vicinity of ferroelectric phase transition has been modeled by the reverse Monte Carlo method. A presence of disordered displacements of Ti atoms due to dynamical tetragonal elongations of unit cells and off-centered sites of Ti atoms in paraelectric phase in the vicinity of the ferroelectric phase transition was observed. Both features result in the anomalous increase of mean square displacements of Ti atoms and reflect the coexistence of displacive and order–disorder components in the ferroelectric phase transition.