IR transmission method applied to the crystallization of gallate glasses and the mechanism of crystallization caused by Ar+ laser and 60Co γ-ray irradiation☆

Abstract The ‘IR transmission method’ combined with the Johnson-Mehl-Avrami equation has been applied to the crystallization study of calcium gallate glasses. The fraction of crystalline phase was approximated by the decreased fraction of IR transmittance. The Avrami index, n , obtained from the Johnson-Mehl-Avrami plot indicated two-dimensional crystallization occurring at the surface layer. Activation energies, E a, of 3.3 and 4.9 eV were obtained from the Arrhenius plot for the surface crystallization of 60CaCO · Fe 2 O 3 and 60CaO · 40Ga 2 O 3 glasses, respectively. By contrast, the Kissinger plot in the ‘DTA method’ yielded E a of 6.3 and 8.9 eV for the bulk crystallization of 60CaO · 39Ga 2 O 3 · Fe 2 O 3 and 60CaO · 40Ga 2 O 3 glasses, respectively. Crystallization by Ar + laser and 60 Co γ-ray irradiations was investigated by means of X-ray diffraction and Mossbauer techniques. CaGa 2 O 4 and Ca 3 Ga 4 O 9 phases were formed by Ar + laser irradiation, whereas CaO and Ga 2 O 3 phases were precipitated in the γ-ray irradiated glass. Thermal energy evolved by the laser irradiation will cause crystallization in the former, whereas a cleavage of the network structure will result in the precipitation of network modifier and former.