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

Abstract

Barium phosphate glasses were prepared with variable Yb2O3 added within 0–3.0 mol% and fixed SnO at 10 mol% (quantities relative to P2O5) to assess physical and spectroscopic properties emphasizing the Sn2+-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/cm3, respectively, with increasing Yb2O3 contents. The glasses were shown to be X-ray amorphous, whereas Raman spectra indicated slight Yb3+-induced phosphate network depolymerization. Optical absorption was consistent with Sn2+ occurrence in the glasses while increasing the Yb3+ concentration. Visible emission spectra obtained under 290 nm excitation concurred with Sn2+ emission wherein the Yb2O3 increments caused continuous Sn2+ PL quenching. The UV to NIR down-shifting promoted by Sn2+ upon 290 nm excitation was favored with increasing Yb2O3 added within 0.5–2.0 mol%, but decreased for 3.0 mol%. From the NIR emission decay curves obtained by exciting Sn2+ at 290 nm, the Yb3+2F5/2 state decay times were estimated which decreased linearly with increasing Yb3+ concentration. Strong Yb3+-Yb3+ interactions following Sn2+ → Yb3+ energy transfer are suggested to be at the origin of the PL weakening observed at the highest Yb3+ concentration.