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

Our present study focuses on examining the thermal, structural and luminescent characteristics of sodium barium metaphosphate glasses doped with Sm. Glass samples with molar compositions (100 - )[(50PO)-(50-NaO)-(BaO)]-SmO, where = 20, 25, 30, 35, 40 and = 0.3 and 1% were first synthesized by conventional melt quenching and later dehydroxylated under a constant N 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 SmO, 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 NaO modifier demonstrated greater influence on Sm 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 SmO concentration from 0.3 to 1 mol%, the experimental lifetimes of the G 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.