We report on the crystallization processes and structure (crystal phases) of Ag33Ge17Se50 glassy alloy using differential scanning calorimetry and x-ray diffraction techniques, respectively. The devitrification that gives rise to the first exothermic peak results in the crystallization of Ag2Se and Ag8GeSe6 phases, while the growth of GeSe2 accompanied by the transformation of Ag8GeSe6 to Ag2Se phase occurs during the second crystallization process. Different theoretical models are used to elucidate various kinetic parameters for the crystallization transformation process in this phase separated system. With annealing below the glass transition temperature, an inverse behavior between the variation of the optical gap and the band tailing parameter is observed for the thermally evaporated films. These results are explained as the mixing of different clusters/species in the amorphous state and/or changes caused by structural relaxation of the glassy network for the thermally evaporated films. (C) 2012 Elsevier B.V. All rights reserved.