The influence of ZnO additions on the structural, optical and thermochemical studies of Li2O-ZnO P2O5 phosphate glasses

In order to explore the effect of ZnO on the structural investigations and calorimetric dissolution of (50-x/2)Li2OxZnO-(50-x/2)P2O5 (0 < x < 25mol%) glass system. Physical parameters show that the replacmement of Li2O by ZnO oxide increases the density, the refractive index, the glass transition and crystallization temperatures.According to the FTIR and 31P NMR-MAS spectrsoscopy, ZnO created the non-bridging oxygen (NBOs) that induces the depolymerisation of phosphate chains.The optical band gap (Eopt) values are in the range between 2.5eV-2.7 eV when x rises. This result may be probably due to the increase in the number of NBOs.The enhancement of the chemical durability was related to the strengthening of the glasses towards water attack and the low mobility of the Zn2+ cations.On the other hand, the microcalorimetric investigations show a decrease of the heat dissolution enthalpy. This behavior was correlated to the shortening of phosphate chains.