The influence of valence states of tungsten ions on PbO–Y2O3–P2O5 glass network

Lead yttrium phosphate glasses mixed with different concentrations of WO3 (ranging from 0 to 5.0 mol%) were synthesized. Differential thermal analysis (DTA), optical absorption, ESR and IR spectral studies have been carried out. The results of DTA have indicated that there is a gradual decrease in the resistance of the glass against devitrification with increase in the concentration of WO3 up to 3.0 mol%. The optical absorption spectra of these glasses exhibited a relatively broad band peaking at about 850 nm identified due to dxy − dx2–y2 transition of W5+ ions; this band is observed to be more intense in the spectrum of glass containing 3.0 mol% of WO3. The ESR spectra of these glasses recorded at room temperature exhibited an asymmetric signal at g⊥ ∼ 1.71 and g|| ∼ 1.62. The intensity of the signal is observed to be maximal for the spectrum of the glass PYPW3. The optical absorption and ESR spectral studies have indicated that there is a maximum reduction of tungsten ions from W6+ state to W5+ state in the glass containing 3.0 mol% of WO3. The IR spectral studies have indicated that there is an increasing degree of disorder in the glass network with increase in the concentration of WO3 up to 3.0 mol%.