Heat treatments versus microstructure in a molybdenum-rich borosilicate

A new glass formulation, a calcium and zirconium-enriched alumino-boro-silicate matrix, able to incorporate 12 wt% of molybdenum oxide has been developed in order to trap molybdenum as CaMoO4, a stable phase in a vitreous medium. Laboratory studies on this matrix have shown the impact of the glass thermal treatment on its microstructure. Thus, four cooling rates and heat treatments presented in this paper were investigated to determine if Ca and Mo totally reacted to give CaMoO4 and to localize the powellite phase in the different glasses. Using X-ray diffraction and Rietveld refinements, we were able to quantify both crystallized and amorphous CaMoO4 in all the samples. EDS analyses allowed us to localize it in the glass microstructure. Then coupling together the micrograph analysis and the X-ray diffraction results proved the presence of amorphous powellite and showed its place in the glasses.