A. Zolatarjovs, A.N. Trukhin, K. Smits, D. Millers Abstract. Crystalline α-quartz doped with 0.1wt% and 0.9wt% germanium was studied using TSL and FGT equipment. Sample was chosen because previously it is known that Ge in quartz is efficient trap for electrons, therefore it could be used for detection of hypothetic self-trapped hole in α-quartz. However […]

L. Grigorjeva, J. Rikveilis, J. Grabis, Dz. Jankovica, C. Monty, D. Millers, K. Smits Photocatalytic activity of TiO2 and ZnO nanopowders is studied depending on the morphology, grain sizes and method of synthesizing. Photocatalysis of the prepared powders was evaluated by degradation of the methylene blue aqueous solution. Absorbance spectra (190–100 nm) were measured during […]

L.Grigorjeva, D.Millers, K.Smits, Dz.Jankovica, L.Pukina Abstract. Time-resolved luminescence and FTIR absorption spectra of undoped and Eu and Ce doped hydroxyapatite nanocrystalline powders prepared by sol-gel method were studied. The luminescence band at 350-400 nm was detected and two decay times (11 ns and 38 ns) was determinated for Ce doped samples. The luminescence spectra and […]

Anatoly N Trukhin, Krishjanis Shmits, Janis L Jansons and Lynn A Boatner Abstract The luminescence of self-trapped excitons (STEs) was previously observed and described for the case of tetragonal-symmetry ScPO4 single crystals. The subject band in this material is situated in the UV spectral range of 210 nm or 5.8 eV. In the present work, […]

U. Rogulis, E. Elsts , J. Jansons , A. Sarakovskis , G. Doke , A. Stunda , K. Smits Tb, Ce, Eu activated oxyfluoride glass-ceramics with the composition SiO2 $ Al2O3 $ Li2O $ LaF3 have been studied by cathodoluminescence (CL). We compared CL intensities and decay times of the Tb, Ce, Eu activated glass-ceramic […]

D. Millers , V. Dimza, L. Grigorjeva, M. Antonova, K. Smits, M. Livins The short lived absorption induced by a pulsed electron beam in the led–lanthanum–zirconate–titanate (PLZT) optical ceramics was studied. The measured absorption spectrum covers 1.1–2.9 eV energy range and consists of several strongly overlapping peaks. The rise of the absorption is delayed with […]

Krisjanis Smits, Dzidra Jankovica , Anatolijs Sarakovskis, Donats Millers The zirconia samples containing two different concentrations of Er and Yb dopants were prepared using the Sol–Gel method and up-conversion luminescence was studied using the time-resolved techniques. The up-conversion luminescence depends on the oxygen content in surrounding gasses during annealing as well as on the annealing […]

A. Sternberg, I. Muzikante, R. Dobulans, D. Millers, L. Grigorjeva, K. Smits, M. Knite, and G. Sakale Abstract The work performed under the National Research Program of Latvia and presented here is about advanced, chemical stimuli responsive materials. Sensor materials are produced on the basis of metallophthalocyanines or zirconia nanocrystals with the purpose of detecting small […]

K Smits, J Liepins, M Gavare, A Patmalnieks, A Gruduls and D Jankovica Abstract. Inorganic nanocrystals are of increasing interest for their usage in biology and pharmacology research. Our interest was to justify ZrO2 nanocrystal usage as submicron level biological label in baker’s yeast Saccharomyces cerevisia culture. For the first time (to our knowledge) images […]

V Liepina, K Smits, D Millers, L Grigorjeva, C Monty Abstract. A novel method – solar induced solid state synthesis – for the synthesis of aluminate phosphor doped with Eu and Dy and the study of its luminescent properties are presented in this article. Two kinds of samples of persistent strontium aluminate phosphor have been […]

L. Grigorjeva , D. Millers , K. Smits , A. Sarakovskis , W. Lojkowski , A. Swiderska-Sroda , W. Strek , P. Gluchowski Transparent Ce and Ce/Pr doped YAG ceramics were prepared under high pressures (up to 8 GPa) and relative low temperature (450 C). Grain size of the ceramics is less than 50 nm. […]

L. Grigorjeva, D. Jankoviča, K. Smits, D. Millers, S. Zazubovich Undoped and rare-earth-ion-doped Y3Al5O12 (YAG) nanopowders are prepared by the sol-gel low-temperature combustion method. The luminescence characteristics of the YAG, YAG:Ce, YAG:Pr, and YAG:Ce/Pr nanopowders are compared with those of the single crystals. The luminescence band peaking around 3.1 eV is complex and excited at […]

A.N. Trukhin, K. Smits , A. Sharakosky , G. Chikvaidze , T.I. Dyuzheva , L.M. Lityagina It is obtained that, as grown, non-irradiated stishovite single crystals possess a luminescence center. Three excimer pulsed lasers (KrF, 248 nm; ArF, 193 nm; F2, 157 nm) were used for photoluminescence (PL) excitation. Two PL bands were observed. One, […]

K. Smits , L. Grigorjeva , D. Millers, A. Sarakovskis, J. Grabis, W. Lojkowski The studies of ZrO2 and yttrium stabilized ZrO2 nanocrystals luminescence as well as yttrium stabilized single crystal luminescence and induced absorption showed that the intrinsic defects are responsible for luminescence at room temperature. These defects form a quasi-continuum of states in […]

Anatoly N. Trukhin , Krishjanis Smits, Georg Chikvaidze, Tatiana I. Dyuzheva, Ludmila M. Lityagina This paper compares the luminescence of different modifications of silicon dioxide – silica glass, -quartz crystal and dense octahedron structured stishovite crystal. Under x-ray irradiation of pure silica glass and pure -quartz crystal, only the luminescence of self-trapped exciton (STE) is detected, […]

Krisjanis Smits , Larisa Grigorjeva a, Donats Millers , Anatolijs Sarakovskis , Agnieszka Opalinska , Janusz D. Fidelus , Witold Lojkowski  The luminescence properties and crystalline structure of ZrO2:Eu nanocrystals doped with different concentrations of Eu were studied. Luminescence from the Eu2+ state was not observed even if the electrons and holes were created up […]

L. Grigorjeva , D.Millers , K.Smits , J.Grabis , J.Fidelus , W. qojkowski , T.Chudoba , K.Bienkowski  The luminescence properties of ZnO ceramics with grains 100-5000 nm sintered by different techniques from nanopowders were studied. The luminescence decay times were compared with that obtained for ZnO singlecrystal. The temperature dependence of non-exponential decay of defect luminescence (2.0-2.6 eV) […]

L. Grigorjeva, D. Millers, A. Kalinko, V. Pankratov, K. Smits Abstract The nanostructured oxide materials such as ZnO, ZrO2, and Y3Al5O12 (YAG) are perspective materials for transparent scintillating and/or laser ceramics. The luminescence properties of single crystals, nanopowders and ceramic were compared. Nominally pure and rare-earth doped nanopowders and ceramics have been studied by means […]

Janusz D. Fidelus and Witold Łojkowski, Donats Millers, Krisjanis Smits and Larisa Grigorjeva Abstract It was shown that ZrO2 nanopowders and nanoceramics can be used as an optical oxygen sensor, where the luminescence signal is proportional to the partial oxygen pressure in gases. The nanopowders were obtained in a hydrothermal microwave driven process followed by annealing […]

L. Grigorjeva , D. Millers , K. Smits , V. Pankratov , W. Łojkowski, J. Fidelus , T. Chudoba , K. Bienkowski , C. Monty  Fast photoluminescence spectra in the spectral region of 3.1–3.45 eV in ZnO and ZnO:Al ceramics were studied at 14 and 300 K. Ceramics with grains smaller than 100 nm were sintered […]

R. Andrew Wall, Kyle C. Lipke, K. B. Ucer, R. T. Williams, D. Millers, K. Smits, and L. Grigorjeva We report transient absorption induced by electron-hole excitation in undoped ZnO. A laser pump/continuum probe method covers 2–300 ps, and an electron pulse with lamp transmission covers 8–300 ns. The broad absorption spectrum increases monotonically with […]

Krisjanis Smits, Larisa Grigorjeva, Donats Millers, Janusz D. Fidelus, and Witold Lojkowski Abstract—The time-resolved luminescence was studied for ZrO:Y single crystal and nanocrystals. The similar recombination centres were found in both—single crystal and nanocrystals. Luminescence decay is within 200 ns in nanocrystals, whereas it extends to the microseconds in single crystal. It was shown that […]

Larisa Grigorjeva, Donats Millers, Janis Grabis, Claude Monty, Aleksandr Kalinko, Krishjanis Smits, Vladimir Pankratov, and Witold Łojkowski Abstract—The luminescence excitation spectra, luminescence spectra and the nanosecond-scale decay kinetics were studied. The ZnO and ZnO:Al nanopowders were prepared by vaporization- condensation in a solar furnace using different raw powders: commercial, hydrothermal and those obtained by plasma […]

Vera Skvortsova, Nina Mironova-Ulmane, Larisa Grigorjeva, Donats Millers, Krisjanis Smits Abstract The transient absorption and luminescence induced by the pulsed electron beam have been investigated in the MgO single crystal containing transition metal ion (Cr, Mn, Fe) impurities and preliminary irradiated by the fast neutrons. It is supposed that the different behavior of the absorption […]

Janusz D. Fidelus, Witold Lojkowski, Donats Millers, Larisa Grigorjeva, Krishjanis Smits and Robert R. Piticescu Abstract: Microwave driven hydrothermal synthesis and hydrothermal synthesis were used to obtain ZrO2 nanopowders. Their production with varying phase composition, the characterisation and selected optical properties concerning their potential use as luminescence oxygen sensors are reported. It was found that […]

Krisjanis Smits, Donats Millers, Larisa Grigorjeva, Janusz D. Fidelus, Witold Lojkowski Abstract. The luminescence spectra of a tetragonally structured ZrO2:Y single crystal and nanocrystals were compared. It was found that the number of luminescence centers contributed to the spectra. The excitation of luminescence within the band gap region led to different luminescence spectra for the single […]

Aleksandr Kalinko, Janusz D. Fidelus, Larisa Grigorjeva, Donats Millers, Claude J. Monty, Adam Presz and Krisjanis Smits Abstract. Pure and Al3+ doped ZnO nanopowders were studied by means of time-resolved luminescence spectroscopy. The powders were synthesized by hydrothermal and plasma methods. These powders were used as a raw material for vaporization-condensation process inside the Solar reactor. […]

Larisa Grigorjeva, Donats Millers, Krishjanis Smits, Claude Monty, Jules Kouam and Lassad El Mir Abstract: ZnO nanocrystals were synthesized and characterized by XRD and SEM methods. The luminescence spectra and decay kinetics were studied under pulsed laser excitation (266 nm, 8 ns). ZnO and ZnO:Al powders were prepared by sol-gel and plasma chemical synthesis. These powders […]

K. Smits, L. Grigorjeva, W. Łojkowski, and J. D. Fidelus The luminescence of undoped tetragonal structure ZrO2 nanocrystals was studied. The luminescence intensity depends on oxygen content in gases mixture in which the nanocrystals were annealed. The distorted Zr-O bond is suggested to be the recombination center for band carriers. The oxygen deficient defect is […]