Structure and molecular modeling of tungsten borotellurate glasses

Glasses of the xWO3 (100−x)[3TeO2·2B2O3] system where x = 0–40 mol% WO3 were synthesized and characterized by investigations on FTIR, UV–VIS, EPR spectroscopy and molecular modeling calculations in order to obtain information about the structural changes of the glass network determined by the evolution of tungsten ions states, glass composition and WO3 concentration.Our spectroscopic data show that the incorporation of WO3 into borate–tellurate glasses causes both the formation of Te–O–W as well as B–O–W linkages and the increase of the number of non-bridging oxygens. The accommodation of the network with the excess of oxygen and the higher capacity of migration of the tungsten ions inside the host network can be associated with a change of tungsten coordination, from [WO4] to [WO6] structural units. This conversion is accompaniment of a large displacement of the tungsten atom from the centre of the octahedral geometry. EPR spectra reveal the existence of two signals associated with the presence of W+5 ions situated in distorted octahedral positions and the oxygen ions defects. The presence of W+5 ions confers to the glass colors that change with composition.

► The [WO6] structural units are highly deformed.
► EPR spectra reveal the existence of W+5 ions situated in distorted octahedral positions and the oxygen ions defects.
► The presence of W+5 ions confers to the glass colors that change with composition.