Devitrification Behavior of Glasses In the System (1-x)Na2O, (x/3)Al2O3, 1.2WO3 (0-less-than-or-equal-to-x-less-than-or-equal-to-0.60)

The materials obtained from the glasses were subjected to differential thermal analysis and x-ray diffraction. Trends in the glass formation and transformation temperatures are explained by the formation of AlO4 tetrahedral units and the consequent increase in the degree of polymerisation. From a kinetic point of view it is suggested that the Al2O3 affects the relative positions of the nucleation and crystal growth temperature ranges until a concentration is reached at which AlO4 units are themselves able to leave the glass network to form crystalline phase during cooling.