Determination of some optoelectrical and thermodynamic parameters of β-lithium ammonium sulphate crystals

Abstract

β-Lithium ammonium sulphate single crystals were grown by slow evaporation solution growth technique. The X-ray diffraction analysis shows that the crystals have an orthorhombic crystal structure with P21cn space group. From the UV–visible spectroscopy, the high transmittance and low reflectance nature of grown crystals was observed. The various optoelectrical parameters like refractive index, extinction coefficient, optical conductivity, electronic polarizability, optical electronegativity and optical band gap were evaluated from the optical transmittance and reflectance data. The Clausius–Mossotti equation and band gap approach were used to calculate the electronic polarizability. The dispersion constants were calculated using Wemple–DiDomenico model and Cauchy dispersion relation. Optical and chemical hardness has been also discussed in terms of polarizability and band gap of the crystals. Some basic thermodynamical variables were also calculated from the thermal analysis. To calculate the activation energy for the decomposition step in these crystals, the Coats–Redfern integral method was used.