Classification of phase transition in perovskite-type dielectric material according to its cubic crystal structure

Electron charge density distributions of perovskite-type dielectric oxides, PbTiO3(ferroelectric), and PbZrO3 and PbHfO3 (antiferroelectric), have been investigated associated with the phase transitions, by analyzing high-energy synchrotron-radiation powder diffraction data by the maximum entropy method (MEM)/Rietveld method. Two distinctive structural features, that is, disordered Pb atom and anisotropic charge density distributions around O atom, are observed only in PbZrO3 and PbHfO3 in the cubic phase. These features can be a clue to understanding why PbZrO3 and PbHfO3 show antiferroelectric phase transition. (author)