OPTICAL PROPERTIES OF SOLID SOLUTIONS IN THE Ag7SiS5I‒Ag7GeS5I SYSTEM

Abstract

The present paper is devoted to the comparison of the determination methods of the optical pseudogap values of Ag7(Si1-xGex)S5I (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) solid solutions by means of two optical spectroscopy techniques: optical absorption and diffuse reflection. Optical absorption spectroscopy was performed on thin single crystalline plane-parallel samples. Diffuse reflectance spectra were obtained on samples in the form of microcrystalline powders (~ 10–20 μm). The optical pseudogap values of Ag7(Si1-xGex)S5I solid solutions, determined on the basis of the logarithmic dependence of the absorption coefficient according to Urbach’s tail range and on the basis of the dependence of the Kubelka-Munk function using the Tauc method. It has been established that the pseudogap energies of the Ag7(Si1-xGex)S5I (x = 0; 0.2; 0.4; 0.6; 0.8; 1) solid solutions obtained by the analyzing the diffuse reflectance spectra of microcrystalline powders and spectral dependences of the absorption index for single crystals do not differ by more than 5% Therefore, it is correct to use a non-destructive and simple method of diffuse reflectance spectroscopy, to estimate the values of the optical pseudogap of porous, poly-, micro- and nanocrystalline objects.