Dzidra Jankoviča

Photoluminescence and photocatalytic activity of zinc tungstate powders

ZnWO4 powders with grain size in range 20 nm–10 µm have been synthesized by a simple combustion method and subsequent calcinations. The photocatalytic activities of powders were tested by degradation of methylene blue solution under UV light. The luminescence spectra and luminescence decay kinetics were studied and luminescence decay time dependence on average powder-grain size was obtained. The correlation between self-trapped exciton luminescence decay time and photocatalytic activity of ZnWO4 powders was shown. A model explaining the excitonic luminescence decay time correlation with photocatalytic activity was proposed.

Characteristic and Sinterability of Alumina-Zirconia-Yttria Nanoparticles Prepared by Different Chemical Methods

The characteristics and sinterability of the Al2O3-ZrO2(Y2O3) nanoparticles produced by simple and effective microwave and molten salts methods and processed by using spark plasma sintering were studied and compared. The crystalline powders with the specific surface area in the range of 72–108 m2/g and crystallite size of 5–13 nm were obtained by calcination of samples prepared by both methods at 800 °C. The content of t-ZrO2 phase depends on concentration of Al2O3, Y2O3 and on calcination temperature but the impact of the preparation method is insignificant. The phase transition of tetragonal ZrO2 to monoclinic for the samples without Y2O3 started at 1000 °C though it was incomplete in the case of high content of Al2O3. The bulk materials with relative density of 86.1–98.7% were fabricated by the spark plasma sintering method at 1500–1600 °C depending on the content of Al2O3 and Y2O3.