High-Energy SR Powder Diffraction Evidence of Multisite Disorder of Pb Atom in Cubic Phase of PbZr1-xTixO3

概要

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High-energy synchrotron-radiation (SR) powder diffraction experiments have been carried out to investigate the relationship between the crystal structure of the paraelectric phase in PbZr1-xTixO3 (PZT) and phase transition. The Rietveld refinement adopting the split-atom method reveals that the Pb atom in PZT, except PbTiO3 ($x=1$), is settled at multisites in relevant directions from the corner site of an ideal cubic structure. Namely, the Pb atom is found to be disordered at 12 sites in the $ \langle 110 \rangle $ directions in PbZrO3 ($x=0$), and at 8 sites in the $ \langle 111 \rangle $ directions in the Zr-rich region ($0<x<0.5$). The disordered motion of the Pb atom markedly changes at $x=0.5$, and the $ \langle 110 \rangle $ disorder is preferable in the Ti-rich region ($0.5<x<1$). The disordered characteristics of the Pb atom and the structural boundary observed at $x=0.5$ in the paraelectric phase are significant for understanding of the mechanism of the order-disorder phase transition and appearance of a morphotropic phase boundary (MPB) in PZT.
2005-09-15