Structure Analysis, Photoluminescence, and Non-linear/Linear Optical Parameters of Li-=SUB=-2-=/SUB=-Ge-=SUB=-4-=/SUB=-O-=SUB=-9-=/SUB=- : Mn-=SUP=-4+-=/SUP=- Transparent Glass-Ceramic

Abstract

In this study, Li2Ge4O9 : Mn4+ transparent glass-ceramic was prepared by conventional melt-quenching. The thermal treatment was used for the devitrification of the sample. The creation of a Li2Ge4O9 nanocrystalline precipitated through the glass matrix was verified by X-ray diffraction and HR-TEM. Electron paramagnetic resonance spectra were employed to confirm the oxidation of Mn2+ to Mn4+ in glass-ceramic after thermal treatment. The photoluminescence spectra displayed a narrow red band centered at 668 nm ascribed to the spin-forbidden 4Eg->4A2g transition of Mn4+. To estimate the optical parameters, UV-Vis-IR absorption spectroscopies were measured. The red shift of the direct optical band gap Eoptg, from 3.81 to 2.55 eV, was observed by increasing the Mn4+ concentration. The dispersion parameters, refraction indices (n, nбесконечность), and oscillator wavelength (λ0) were examined by using Wemple--DiDomenico single-oscillator model. The relationship between the refractive index and the energy gap has been investigated using various models such as Moss, Herve--Vandamme, Ravindra, and Singh--Kumar. In addition, the linear and non-linear optical properties of Li2Ge4O9 : Mn4+ were mentioned. The temperature-dependent luminescence intensity measurement was also carried out. The method of preparation exposed herein for the synthesis of Mn4+-doped GCs might be prevailing to produce identical luminescent ceramics in accordance with the glass's devitrification. Keywords: glass-ceramics, photoluminescence, optical properties, non-linear/linear optical, dispersion parameters, energy gap