High-Temperature Structural Studies of SrPbO3 and BaPbO3

Abstract

High-resolution X-ray powder diffraction studies have shown BaPbO₃ to transform from an orthorhombic Imma structure at room temperature, through an intermediate I4/mcm phase, to a cubic Pm3–mstructure above 500°C. The Imma to I4/mcm transition is first order and the I4/mcm–Pm3–m transition for BaPbO₃ is tricritical in nature. We find no evidence for any phase transitions in SrPbO₃ up to 760°C, the structure remaining in Pnma from room temperature to 760°C.