Influences of ZnO on the chemical durability and thermal stability of calcium iron phosphate glasses

This study aims to investigate influences form zinc oxide on glasses in xZnO-(100-x) (54P2O5-36Fe2O3-10CaO) (x = 3,6,9,12,15,18 mol%). Structure analyses were carried by FTIR, and chemical durability tests were introduced to study changes in dissolution rate and weight losses. Thermal stability properties were measured and discussed through DSC. Results from structure changes indicate that glass network turns less compact with more ZnO, the building units gradually evolving into Q0 groups from Q1 tetrahedra, even the whole glass system locates in orthophosphate glasses. Higher melting temperature results in more Fe2+ that would lead to octahedral and disordered octahedral in the prepared glasses also contributing to open glass network in glass structure. The resistance in both alkali and acid solution were deteriorated for the sake of the open network, accompanied with the less strong P-O-Zn bonds when compared with the P-O-P bonds. Reasons accounting for the weak resistance also refer to the transition from [ZnO6] to [ZnO4], larger volume of [ZnO4] than that of [PO4], small particle size in ternary phosphate glasses. Drops in weight loss for each test span with corrosion time might be owing to the formation of alter layer on the surface of glass samples during corrosion. The phenomenon in water also follow the similar trend as those in the other two solutions for the same reasons. The glass transition and crystalline temperatures of all glasses drop as the degree of polymerization in glass becomes small, with four glass stability parameters falling as the amount of ZnO rises.