Influence of vanadium in sensitized luminescence mechanism and Judd-Ofelt analysis in Er3+/Ho3+ doped mixed ionic-electronic glass system

Er3+/Ho3+ Doped Al₂O₃-Na₂O–TeO2 mixed ionic-electronic glasses containing different concentrations of V₂O5 ranging from 0 to 2.0 mol% were prepared using melt-quenching method. The structural, optical and photoluminescence properties of the glass were studied using FTIR, UV–Vis, and photoluminescence spectroscopy measurements. XRD analysis confirms the amorphous nature of the glass system. The relative areas of TeO4 and TeO3 were measured to demonstrate the correlation of bridging/non-bridging oxygen that exist in the glass network. It was observed that the relatively high TeO3 indicates that the environment of the glass system is NBO-rich despite the increase in BO attributed to V2O5. Analysis on optical absorption edge by Tauc's plot revealed that EOpti decreases due to the prevalence of NBO in the glass system. The Judd-Ofelt oscillator strength, fexp increases accompanied with an anomalous drop at x = 1.0 mol% due to the competition between BO and NBO that has altered the covalency and asymmetry of the Er3+ with the local environment ligand. Meanwhile, the Judd-Ofelt parameter Ω2 decreases generally suggesting that the glass system has underwent some structural modification due to the increase in BO in the host matrix contributed by the VO5. Photoluminescence spectra revealed three dominant emissions in the green region (525 nm;2H11/2 ➝ 4I15/2, 532 nm; 5F4 + 5S2➝ 5I8, 547 nm;4S3/2 ➝ 4I15/2) and 2 emissions in the red region (659 nm; 5F5 ➝ 5I8, 662 nm; 4F9/2 ➝ 4I15/2). As vanadium increased, a decrease in photoluminescence intensity is observed as a result of concentration quenching between V4+ and Ho3+.