Influence of barium substitution on the physical, thermal, optical and luminescence properties of Sm3+-doped metaphosphate glasses for reddish orange light applications

Abstract

Our present study focuses on examining the thermal, structural and luminescent characteristics of sodium barium metaphosphate glasses doped with Sm³⁺. Glass samples with molar compositions (100 − y)[(50P₂O₅)–(50-xNa₂O)–(xBaO)]–ySm₂O₃, where x = 20, 25, 30, 35, 40 and y = 0.3 and 1% were first synthesized by conventional melt quenching and later dehydroxylated under a constant N₂ flow to ensure final glasses with a very high degree of chemical and optical homogeneity and free of water. Upon the addition of BaO and Sm₂O₃, refractive index, molar mass, density, glass transition temperature and dilatometric softening temperature exhibited an increase, whereas the coefficient of thermal expansion showed a decrease. The FTIR spectra analysis reveals a network depolymerization that intensifies with rising BaO concentration, ultimately transitioning from a modifier oxide to a glass-forming element, at higher BaO concentrations. All doped samples exhibited prominent absorption bands in the visible (VIS) and near-infrared (NIR) regions, as revealed by the optical absorption spectra. The Na₂O modifier demonstrated greater influence on Sm³⁺ emission compared to BaO, a phenomenon that can explained by the moderation of the local ligand field strength resulting from this substitution. With an increase in Sm₂O₃ concentration from 0.3 to 1 mol%, the experimental lifetimes of the ⁴G_5/2 level decrease, primarily attributed to the presence of energy transfer mechanisms. A discussion of Judd–Ofelt parameter analysis and glass radiation properties will be presented.