Using X-ray diffraction and differential scanning calorimetry (DSC) the structure and the crystallization mechanism of Se0.8Te0.2 chalcogenide glass have been studied. From the radial distribution function, the short-range order of the amorphous phase has been discussed. The lattice parameter of the crystalline phase has been determined by using the Cohen least-squares method. The results of the thermal analysis indicate that the crystallization process is a two- dimensional growth. The calculated value of the effective activation energy for crystal growth, EG, is 160.8 ± 0.1 kJ/mol. The calculated lattice parameters a and c of the hexagonal crystalline phase are 0.4398 ± 0.0014 and 0.5055 ± 0.0021nm, respectively.

Results of differential scanning calorimetry (DSC) at different heating rates on Se0.8Te0.2chalcogenide glass are reported and discussed. From the variation of heating rate (a ) the crystallization fraction (x), heat flow difference (D q) and the crystallization peak temperature (Tp), the value of the effective activation energy for growth (Eg) was evaluated by six different methods. The Se0.8Te0.2 chalcogenide glass has two crystallization mechanisms, one-dimensional and surface crystallization growth. The average value of Eg for Se0.8Te0.2 chalcogenide glass is equal to (123.5 ± 5.7) kJ/mol. All the methods used to evaluate the effective activation energy for growth (Eg) are valid to discuss the results of glass-crystalline transformation but with differing accuracies.

Results of differential thermal analysis (DTA) under nonisothermal conditions on five chalcogenide glasses of the InxSe1-x system (x = 0.05, 0.10, 0.15, 0.20 and 0.25 at.) are reported and discussed. The crystallization mechanism has been studied by using DTA, scanning electron microscopy (SEM) and X-ray diffraction. From the dependence of the glass transition temperature (Tg), the onset crystallization temperature (Tc) and the crystallization peak temperature (Tp) on the heating rate (a ), the glass transition activation energy (Et) and the crystallization activation energy (Ec) were derived. The calculated Et for InxSe1-x varied between 246 and 309 kJ/mol. The results indicate that bulk crystallization with two-dimensional growth occurs for these glasses. The average activation energy of crystallization for InxSe1-x varied between 105 and 125 kJ/mol. In0.10Se0.9 chalcogenide glass showed a minimum value of Ec as well as (Tc - Tg), which represents the thermal stability of the glass, indicating that this composition has a tendency towards crystallization more than the other compositions.

The effect of Mg content on some of the electrical parameters and the microhardness of Al-Mg alloys has been investigated. Namely, the dependence of the temperature coefficient of resistivity, a all, the electronic relaxation time, t all, and the electron-impurity scattering power, D h , on the Mg content in the alloys has been studied. On the other hand, the influence of dissolved Mg on the microhardness ofAl- Mg alloys has been evaluated. In addition, the decomposition behaviour of the supersaturated Al-Mg alloys has been followed and characterized.

Results on the thermal analysis, switching characteristics and effect of heat treatment on the structure and electrical resistivity of the chalcogenide glass As25Si45Te30 are reported and discussed. From the dependence of the crystallization peak temperatures, Tp, on the heating rate, the crystallization activation energies were evaluated. For the investigated composition, the most probable mechanisms for the two crystallization phases are three- and one-dimensional crystal growth. Transformation from the glassy structure to the crystalline phase was responsible for the decrease in room-temperatire resistivity and activation energy for conduction with increase of the annealing temperature. Memory-type switching was observed in the chalcogenide glass As25Si45Te30.

The short- and medium-range orders of GeSe2 chalcogenide glass were studied by using the radial distribution function. The effect of the annealing temperature on the short-range order structure of this glass was investigated. The short-range order structure of as-prepared and annealed GeSe2 chalcogenide glass is regular tetrahedron (edge and corner sharing GeSe4 tetrahedra). The medium-range order of the GeSe2 chalcogenide glass is chemical order associated with topological order. The topological structure of the medium-range order can be described by the Phillips model. The basic structure unit does not change after annealing. Most changes observed in the diffraction patterns may be interpreted in the framework of structural relaxation during which a system tends to attain a metastable equilibrium state. This relaxation can be described by an a process.

The thermophysical properties (thermal diffusivity a, specific heat Cp and thermal conductivity l ) of Bi1.5Sb0.5Te3 were measured in the temperature range 300-700 K. The results showed that the contribution of the charge carriers to the thermal conduction is negligibly small in com- parison with the contribution of phonons at high temperatures. On the other hand, the heat conduction due to the simultaneous thermal diffusion of electrons and holes is important as well as the lattice thermal conduction. The explanation of the results was supported by using electrical conductivity measurements and X-ray diffraction.

In the present work, the structure of Aso.3Seo.2So.4Geo.1 chalcogenide glass has been studied using the radial distribution function (RDF). Moreover, the effect of annealing temperature on the short range order of this glass has been investigated. The results revealed that the short range order structure of the as-prepared and annealed Aso.3Seo.2So.4Geo.1 chalcogenide glass is close to a regular tetrahedron. The medium range order of Aso.3Seo.2So.4Geo.1 chalcogenide glass is topology order. The topological structure of the medium range order can be described by the Phillips model. The structure of Aso.3Seo.2So.4Geo.1 chalcogenide glass is stable in the annealing temperature range 324-523 K.

Using X-ray diffraction and differential scanning calorimetry (DSC), the structure and the crystallization mechanism of Se0.7Te0.3 chalcogenide glass have been studied. By means of the radial distribution function, the short-range order of the amorphous phase has been discussed. The lattice parameters of the crystalline phase have been determined by using the Cohen least-squares method. The crystallization mechanism and the activation energy have been investigated by using the Ozawa and the Takhor methods, respectively. The calculated lattice parameters a and c of the crystalline phase are 0.4380 ± 0.0015 and 0.5198 ± 0.0027 nm, respectively. On the other hand, the results of the thermal analysis indicate that the crystallization process is a two-dimensional growth. The calculated value of the activation energy for crystal growth EG is 161.7 ± 0.6 kJ/mol.