Anomalous dispersion X-ray diffraction study of Pb/Bi ordering/disordering states in PbTiO-based perovskite oxides.

Synchrotron radiation-based anomalous dispersion X-ray powder diffraction (ADSPD) was carried out to reveal the Pb/Bi ordering/disordering states in a series of PbTiO-based negative thermal expansion materials (1 - x)PbTiO - xBiFeO (x = 0.1, 0.3, 0.5) and (1 - x)PbTiO - xBi(ZnTi)O (x = 0.1, 0.2, 0.3). It gives strong evidence of the disordered Pb/Bi distributions in these compositions, which is consistent with electron diffraction studies. Combined with binding energy calculation, we show that the disordered nature of Pb/Bi distributions is likely to be attributed to the similar electron configurations of Pb and Bi as well as their comparable coordinate environments in perovskite structures. The results of this study may be helpful to better understand the structure-property relationship in Pb/Bi-containing perovskites and are useful for further developing underlying physics in relevant materials.