Effect of Fe2O3 content on the local structure and crystallization mechanism of calcium gallate glasses

Fe-57 Mossbauer and FT-IR of 60CaO.(40-x)Ga2O3.xFe(2)O(3) glasses revealed that Fe(III)O-4 tetrahedra occupy substitutional sites of Ga(III)O-4 tetrah edra. The activation energy for crystallizaation (E-a) obtained from DTA st udy decreases distinctly from 8.9 to 4.8 eV with an increase in the Fe2O3 c ontent. In the case of 40CaO.(60-x)Ga2O3.xFe(2)O(3) glasses, a week doublet due to Fe(II)O-4 tetrahedra or Fe(III)O-6 octahedra was observed in additi on to Fe(III)O-4 tetrahedra. The E-a value decreases gradually from 7.1 to 5.6 eV with an increasing Fe2O3 content. These results indicate that a larg e amount of Fe2O3 in the network structure is favorable for the crystalliza tion of calcium gallate glass, since it reduces the chemical bond strength.