الفهرس 
Introduction and Literature Review
IntroductionOnly 14 pages are availabe for public view
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Abstract
The purpose of this thesis is to determine the structural and optical properties of Se90-xTe10Snx (where x= 0, 2.5, 5 and 7.5 at. %)glasses. The amorphous materials of bulk samples of the Se90-xTe10Snx glasses were prepared by the usual melt-quenching technique. The films of the Se90-xTe10Snx glasses were deposited onto ultrasonically cleaned glass substrates by thermal evaporation technique under vacuum of 10-5 Torr. Results of differential thermal analysis (DTA) under nonisothermal conditions of Se90-xTe10Snx (x = 0, 2.5, 5 and 7 at %) glasses are reported and discussed. The glass transition temperature (Tg), the onset crystallization temperature (Tc) and the peak temperature of crystallization (Tp) were found to be dependent on the compositions
and the heating rates. It’s seen that all glasses have a single glass transition and single stage crystallization on heating rates. Values of various kinetic parameters such as activation energy for glass transition Et), activation energy of crystallization (Ec), Hurby number (Hr) and the order parameter (n) have been determined. The results indicate that the rate of crystallization is related to the thermal stability and the glass forming ability (GFA) in the present glasses. The decrease in Et with increasing Sn content while increase of Ec with increasing Sn content.The crystallization parameters were calculated using different models. The activation energies of the amorphous- crystallize phase transformations (Ec) were calculated for the studied compositions using several models based on the JMA model. These results indicate a considerable difference in the values of Ec deduced by different formulations. This may due to different approximations that have been adopted for finding the final equations of the various formalisms.