Effect of thermal annealing on the spectroscopic parameters of Er3+-doped sodium silicate glass

This paper presents the optical characteristics of Er³⁺ ions in sodium silicate glass (SiO₂–Na₂O), synthesized by the fusion method and later annealed for 0, 30, 60 and 90 min. Thermograms, X-ray diffraction, optical absorption, luminescence spectroscopy measurements were performed in order to determine the thermal and structural of the samples and the radiative characteristics of Er³⁺ ions under influence of thermal annealing of the samples. Differential thermal analysis provided evidence of a phase change in the system. This phase change was confirmed by X-ray diffraction, which showed the formation and growth of Na₂SiO₃ crystals for the annealed samples. These crystals affect the neighborhood (from second vicinity) of Er³⁺ ions. These effects were noted by the J–O parameters (Ω₂ and Ω₄), which were calculated from the optical absorption spectra. Judd–Ofelt calculations also confirmed that heat treatment induced structural rearrangement of the samples that was dependent on Er₂O₃ concentration. This resulted in changes in the optical and physical properties of the samples, including stimulated emission cross section and rigidity. Analysis of the spectroscopy parameters after of thermal annealing indicate samples are potential materials for in optical device applications.