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Subject classification: 61.43.Fs; 78.30.Ly; S10.15 PbO-As 2 O 3 glasses containing different concentrations of WO 3 (ranging from 0 to 1 mol%) were prepared. A number of studies, namely, differential thermal analysis, IR spectra, optical absorption, ESR, elastic properties (Young's modulus E, shear modulus G and microhardness H) and dielectric properties (dielectric constant e, loss tan d, and ac conductivity s ac , over a range of frequency and temperature and breakdown strength), were carried out on these glasses as a function of tungsten ion concentration. An anomaly has been observed in all the properties of these glasses when the WO 3 concentration is about 0.4 mol%. The studies indicate the presence of W 5+ O À 3 complexes in the glass matrix when the concentration of WO 3 is more than 0.4 mol%. The analysis of results suggests that the stability of the PbO-As 2 O 3 glass network is enhanced if a small concentration of WO 3 (about 0.4 mol%) is present in the glass matrix.

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