Polishchuk Y. Structure evolution of highly-dispersed ZrO2 and ZnS materials during synthesis and annealing

The dissertation presents the results of research of powder structures of ZrO2 and ZnS:Cu and ZnS:Mg nanocrystals. The basic methods of analysis of powder-like structures are considered. The methods of identification of phases and methods of quantitative and qualitative analysis with use of crystallographic databases and methods of calculation of dimensions of coherent scattering area are considered. In this work, the influence of annealing temperature, cooling and doping regime on different impurities on the structural properties of powders based on ZrO2 and ZnS was investigated. When analyzing powders based on ZrO2, it was found that the cooling rate does not affect the structural features of the tested specimens. It has been established that at constant annealing temperature, the increase in Y content stimulates the phase transition from the monoclinic phase, through tetragonal to cubic, and also reduces the size of nanocrystals. In samples based on ZrO2 doped with different amounts of Cu, the change in the annealing temperature stimulates copper penetration, which occurs as a result of the destruction of Cu-containing surface complexes; and the output of copper, which leads to t-c-m transformations and the appearance on the grain surface of CuO. These two main processes also depend on the content of Cu. The crystalline structure of ZnS powders by RD methods was investigated. The obtained results are consistent with the research of these powders by the EPR method, in which it was found that the EPR method is more sensitive to the cubic phase and allows to establish the presence of a local distortion of the crystal lattice The zinc sulfide based powders investigated the effect of Zn/S in the charge, and doping. It was found that the size of the grain does not depend on the composition of the charge and the contribution of the cubic phase increases with the increase in the content of sulfur in the charge. The influence of annealing at 800°C on the structural characteristics of the powdered ZnS:Cu has been investigated. It has been established that annealing results in a change in the composition of ZnS powder, which depends on the heating time and annealing temperature: a decrease in the content of the hexagonal phase of ZnS and an increase in the cubic phase, the appearance and increase of the content of the ZnO phase. It is shown that the oxidation process is anisotropic and more pronounced for the hexagonal phase of ZnS. The change in the size of the OCR in both phases of ZnS determines the anisotropic nature of the phase transformation of ZnS