Revealing phase boundaries by weighted parametric structural refinement

Abstract

Parametric Rietveld refinement from powder diffraction data has been utilized in a variety of situations to understand structural phase transitions of materials in situ. However, when analysing data from lower‐resolution two‐dimensional detectors or from samples with overlapping Bragg peaks, such transitions become difficult to observe. In this study, a weighted parametric method is demonstrated whereby the scale factor is restrained via an inverse tan function, making the phase boundary composition a refinable parameter. This is demonstrated using compositionally graded samples within the lead‐free piezoelectric (BiFeO3)x(Bi0.5K0.5TiO3)y(Bi0.5Na0.5TiO3)1–x–y and (Bi0.5Na0.5TiO3)x(BaTiO3)1–x systems. This has proven to be an effective method for diffraction experiments with relatively low resolution, weak peak splitting or compositionally complex multiphase samples.