Crystallization in silicate glasses containing molybdenum and phosphorus

The addition of some oxides in a glass that was initially homogeneous can lead to more or less important crystallization processes during glass cooling. Among the oxides well known to induce crystallization there are molybdenum oxide MoO3 and phosphorus oxide P2O5. This study based on glasses containing SiO2, Na2O and CaO has allowed us to understand the role of molybdenum and phosphorus in crystallization. The identification and quantification of crystal phases has been made by using electron scanning microscopy and X-ray diffraction. It seems that phosphorus decreases the solvability of molybdenum in a silicated crystal structure. The silicated area is then poor in molybdenum and as a consequence molybdenum concentrates in other areas that can turn themselves into crystal growth zones of molybdates. (A.C.)