Contribution to the study of some materials

Abstract

V první části práce jsou shrnuty výsledky studia skel systému ge-S pomocí elektronové paramagnetické rezonance a fotolumuniscence.V druhé části jsou uvedeny výsledky získané při použití některých metod termické analýzy při studiu řady nekrystalických materiálů. vedle toho je ukázána také možnost aplikace těchto metod při studiu dehydratace interkalátu VOPO42H2O.Presented habilitation thesis contains two parts. The first one deals with the study of intrinsic defect centers of semiconducting Ge-S glassy system. The result of this part is the proposal of new model of intrinsic paramagnetic defects. The Ge-related signal was found in glasses of whole glass-forming region. This signal was assigned to a two-atomic defect center which is formed by the interaction of broken bonds of Ge with two-coordinated sulfur atoms forming (Ge4...S3)o centers. A multiline spectrum was found not only in Ge-S sulfur rich glasses but also in glassy sulfur after excitation by Ar+ laser. This signal can be assigned to two defect centers: (S2...trans-S3)o and (S2...cis-S3). On the basis of this model is possible to explain non-occurrence of similar paramagnetic defect centers in other chalcogenide glassy systems (for example Ge-Se, As-S, As-Se) as well. The second part concerns with thermoanalytical properties of materials. Kinetic of both isothermal and non-isothermal crystallization was studied by Differential scanning calorimetry for undercooled melts of selenium and As-Se system. Influence of Johnson, Mehl, Avrami kinetic exponent n on determination of the proper kinetic model was demonstrated. Application of Differential scanning calorimetry, Thermogravimetry, Thermomechanical analysis and Dynamic differential scanning calorimetry on thermal stability of materials (for example glasses, crystals, intercalates) was used.Dokončená práce s úspěšnou obhajobo