Off-centering of a Bi ion in cubic phase of (Bi1/2Na1/2)TiO3

The paraelectric cubic structure of (Bi_1/2Na_1/2)TiO₃ was analyzed precisely by high-energy synchrotron radiation X-ray powder diffraction measurement and the maximum entropy method (MEM)/Rietveld method. The <100>-favored rotator-like thermal behavior of the Bi ion was observed. The <100> off-centering of Bi led to the Bi-O distance of ∼2.5 Å that was shorter than the average Bi-O distance in the structure of the Bi on-centered model. The off-centering of Bi can be attributed to the orbital hybridization between the Bi and O ions.