Structural properties of the tungsten–lead–borate glasses before and after laser irradiation

Glasses in the xWO3·(100 − x)[3B2O3·PbO] system, where 0 ≤ x ≤ 40 mol%, are obtained by conventional melting–quenching method and characterized using X-ray diffraction, FTIR spectroscopy and DFT calculations. These tungsten–lead–borate systems exhibit a photochromic effect which can be induced through laser exposures (λ = 633 nm) directly on the bulk sample. Structural investigations show that the photosensitive effect are due to a reduction of W+ 6 to W+ 5 and/or W+ 4 promoted by the oxidation of Pb+ 4 and some structural changes of the borate network. DFT calculations show higher thermodynamic stability of the [W2O7] and [WO4] polyhedrons comparative with the [WO6] polyhedron.