Investigation of structural and optical properties of lanthanum gallates

Abstract

Polycrystalline LGO sample has been prepared using modified chemical wet route. In order to know the structural phase purity of the prepared sample, X-ray diffraction has been carried out. Band gap of prepared sample has been determined using Diffuse Reflectance Spectroscopy (DRS) which is obtained through the mathematical relation of Kubelka-Munk function, known as Tauc plot. Behavior of band gap with temperature has been studied using temperature dependent DRS experiments. These materials show the structural phase transition from orthorhombic to rhombohedral at around 417 K temperature. In order to know about the kind of structural phase transition present in the sample, temperature dependent DRS has been carried out. On the further confirmation of structural phase transition, temperature dependent Raman spectroscopy has been carried out. Variation of Urbach energy with temperature has been also studied using TD DRS. Additionally, Temperature dependent optical band gap has been fitted using various fitting models like Varshni model and Bose-Einstein model to determine the thermodynamics of prepared sample. Both TD Diffuse Reflectance Spectroscopy and TD Raman spectroscopy confirms that LGO shows a structural phase transition from orthorhombic to rhombohedral phase at around 417 K temperature.