Influence of Mn2+ doping on refractive and electronic properties of β-LiNH4SO4 crystals

Abstract

β-LiNH4SO4:Mn2+ crystals with 2 and 5 wt% Mn2+ concentration have been synthesized. The crystalline structure of impurity crystals was identified and refined by means of X-ray diffraction analysis. Experimentally studied dispersions of the refractive indices and birefringence showed that the introduction of the impurity leads to an increase in the absolute values of refractive indices without changing the nature of the dispersion; the anisotropy of the optical indicatrix increases along with a significant changes of birefringence absolute values. The optical birefringence temperature dependence reveals shifts in the phase transition point of the impurity crystals towards lower temperatures; the temperature interval of the existence of the “intermediate” phase in the β-LiNH4SO4:Mn2+ also shifts. The results of optical studies are independently confirmed by experimental studies of thermal expansion and differential thermal analysis. Band structure and optical spectra of β-LiNH4SO4:Mn2+ crystal are calculated using the density functional theory.