Electron charge density distributions of perovskite-type dielectric oxides, PbTiO
3 (ferroelectric), and PbZrO
3 and PbHfO
3 (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 PbZrO
3 and PbHfO
3 in the cubic phase. These features can be a clue to understanding why PbZrO
3 and PbHfO
3 show antiferroelectric phase transition.
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