Thermal, structural and optical properties of new tungsten lead–pyrophosphate glasses

Crystalline lead–pyrophosphate precursor was prepared in aqueous solution from lead nitrate and phosphoric acid and characterized by X-ray diffraction, thermogravimetry and Raman scattering. This crystalline lead–phosphate was then used to prepare glass samples in the binary system Pb 2 P 2 O 7 –WO 3 . Dependence of WO 3 content on thermal, structural and optical properties were investigated by thermal analysis (DSC), Raman spectroscopy, UV–visible and near-infrared absorption and M-Line technique to access refractive index values. Incorporation of WO 3 in the lead–pyrophosphate matrix enhances the glass transition temperature and thermal stability against devitrification, favors formation of P O W bonds and WO 6 clusters. In addition, optical properties are strongly modified with a redshift of the optical bandgap with WO 3 incorporation as well as an increase of the refractive index from 1.89 to 2.05 in the visible.