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

High energy planetary ball milling has been used to synthesize pseudo-cubic highly-pure LaGaO 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 GaO tilting. Rietveld analysis, Raman spectroscopy, and transmission electron microscopy were used to elucidate the LaGaO structures at different temperatures.This work was supported by the Spanish Government financed in part by the European Regional Development Fund through the Ramón y Cajal Program RYC-2013-12437