Physical and spectroscopic properties of variable Yb2O3 doped phosphate glasses containing SnO as UV sensitizer for Yb3+ NIR emission

Barium phosphate glasses were prepared with variable Yb ₂O ₃ added within 0–3.0 mol% and fixed SnO at 10 mol% (quantities relative to P ₂O ₅) to assess physical and spectroscopic properties emphasizing the Sn ²⁺-promoted ultraviolet (UV) to near-infrared (NIR) photoluminescence (PL) down-shifting. The various characterizations performed involved refractive index (D-line), density, X-ray diffraction, Raman spectroscopy, UV–Vis–NIR absorption, and PL spectroscopy (steady-state & dynamic) measurements. The refractive indices and densities increased within the ranges of ∼1.60–1.62 and ∼3.70–3.83 g/cm ³, respectively, with increasing Yb ₂O ₃ contents. The glasses were shown to be X-ray amorphous, whereas Raman spectra indicated slight Yb ³⁺-induced phosphate network depolymerization. Optical absorption was consistent with Sn ²⁺ occurrence in the glasses while increasing the Yb ³⁺ concentration. Visible emission spectra obtained under 290 nm excitation concurred with Sn ²⁺ emission wherein the Yb ₂O ₃ increments caused continuous Sn ²⁺ PL quenching. The UV to NIR down-shifting promoted by Sn ²⁺ upon 290 nm excitation was favored with increasing Yb ₂O ₃ added within 0.5–2.0 mol%, but decreased for 3.0 mol%. From the NIR emission decay curves obtained by exciting Sn ²⁺ at 290 nm, the Yb ^{3+ 2}F _5/2 state decay times were estimated which decreased linearly with increasing Yb ³⁺ concentration. Strong Yb ³⁺-Yb ³⁺ interactions following Sn ²⁺ → Yb ³⁺ energy transfer are suggested to be at the origin of the PL weakening observed at the highest Yb ³⁺ concentration.