Isosymmetric structural phase transition of the orthorhombic lanthanum gallate structure as a function of temperature determined by Rietveld analysis

Abstract

High energy planetary ball milling has been used to synthesize pseudo-cubic highly-pure LaGaO₃ in one hour from its oxide components in an air atmosphere. Calcination at different temperatures led to the crystallization of lanthanum gallate in an orthorhombic structure with its local lanthanum coordination number environment changing from 12 to 7 when the temperature was increased. This change was attributed to the thermal expansion of the Ga–O bonds that varied non-monotonically inducing GaO₆ tilting. Rietveld analysis, Raman spectroscopy, and transmission electron microscopy were used to elucidate the LaGaO₃ structures at different temperatures.