Role of molybdenum on the structure and properties of A2O-P2O5-MoO3 (A = Na, Ag, Rb, Cs) glasses

Molybdenum phosphate glasses are materials of interest for nuclear waste storage and solid-state electrolytes, amongst others. Thermal and electrical properties of vitreous molybdophosphates are highly dependent on molybdenum local environment while for example the coordination of this transition metal is still a matter of discussion. The structure of glasses of following composition, xMoO3-(100-x)APO3 (with A = Ag, Na, Rb and Cs) was investigated by means of 31P and 95Mo Nuclear Magnetic Resonance spectroscopy. The structural information was used to better understand the evolution of thermal properties as a function of the molar fraction of MoO3. Particular attention was paid to the crystallization mechanism, studied by X-ray Diffraction, High Temperature Environmental Scanning Electronic Microscopy and Kissinger model, highlighting the formation of a molybdate network (Mo-O-Mo bonds).