Characterization studies of molybdophosphate glasses and a model of structural defects

Abstract

Glasses in the system MoO₃P₂O₅K₂O have been studied over a wide range of compositions. Molar volumes, microhardnesses, glass-transition temperatures, heat capacities and infrared spectra of selected compositions have been measured and reported. A structural model has been proposed for these glasses in which the basic feature is the presence of an extensive network of corner shared [MoO 6/2] octahedra and [POO 3/2] tetrahedra. The effect of added K₂O which degrades such a network and creates unshared corners has been considered in detail. The nature and concentration of various defects which depend upon glass composition and relative energies of the covalent linkages have also been considered in detail. The defects are consolidated into a structural-phase diagram which has been used to interpret the observed properties. The loss of oxygen during the preparation of glasses and its consequence upon the structure have also been discussed.