Structure of TeO2 · B2O3 glasses inferred from infrared spectroscopy and DFT calculations

Glasses in the system (1 − x)TeO2 · xB2O3 glasses (with x = 0.3 and 0.4) have been prepared from melt quenching method. The structural changes were studied by FTIR spectroscopy and DFT calculations. From the analysis of the FTIR spectra it is reasonable to assume that when increasing boron ions content the tetrahedral [BO4] units are gradually replaced by trigonal [BO3] units. The increase in the number of non-bridging oxygen atoms would decrease the connectivity of the glass network, would depolymerize of borate chains and would necessite quite a radical rearrangement of the network formed by the [TeO6] octahedral. This is possible considering that tellurium dioxide brings stoichiometrically two oxygen atoms in [TeO4] and needs an additional oxygen atom for the formation of [TeO6] octahedra. This additional oxygen atom is evidently taken off from the boron co-ordination and thus boron atoms transfer their [BO4] co-ordination into [BO3] co-ordination. We used the FTIR spectroscopic data in order to compute two possible models of the glasses matrix. We propose two possible structural models of building blocks for the formation of continuous random network glasses used by density functional theory (DFT) calculations.