Effects of substituting P_2O_5 for B_2O_3 on the thermal and optical properties of sodium borophosphate glasses doped with Er

摘要

In this paper a set of (95-x) P_2O_5-xB_2O_3-4.9Na_2O-0.1Er_2O_3 (x = 5-10-15-20 mol%) samples was prepared using a conventional melt-quenching technique. A glass ceramic phase was confirmed by X-ray diffraction. Small crystallites at the B_2O_3 addition were detected by Raman scattering. The glass containing 20 mol% B_2O_3 shows a high thermal stabilitywith a value ΔT=T_c-T_g exceeding 100 °C,where T_g and T_c are the glass transition and crystallization onset temperatures. The Raman spectroscopy measurement shows that BOP bondswere present in the glasses. Fromthe absorption edge studies, the value of the optical band gap Eopt has been evaluated. The decrease in optical band gap values and consequently the decrease in Urbach's energies confirm the less extension of the localized states within the band gap. As a result, there shall be an increase in the order of the glass network. The variation in optical parameters is owing to the substitution of B_2O_3 oxides in P_2O_5-Na_2O-Er_2O_3 glass network. The fundamental absorption edge for all the glasses was analyzed and the Judd-Ofelt parameters (Ω_2, Ω_4 and Ω_6) were obtained. The PL intensity, the PL life time and the quantum efficiency relative to the ~4I_(13/2) → ~4I_(15/2) (1530 nm) transition of Er~(3+) were all found to decrease with the addition of B_2O_3.