Direct observation of covalency between O and disordered Pb in cubic PbZrO3

In cubic PbZrO3, which undergoes an anti ferroelectric phase transition, the distinct disorder of Pb at twelve sites toward the neighboring O is detected for the first time by analyzing high-energy X-ray powder diffraction data. In the charge density distributions, the covalent nature of the Pb-O bond is also revealed, which proves the existence of electron hybridization between O and disordered Pb in cubic PbZrO3. None of these structural characteristics of PbZrO3 were found in the previously studied cubic PbTiO3 structure [Y. Kuroiwa et al.: Phys. Rev. Lett. 87 (2001) 217601], which undergoes a ferroelectric phase transition. This may be a clue to understanding why PbTiO3 and PbZrO3 respectively show ferroelectric and antiferroelectric phase transitions.