Просмотр по автору "Krieke, Guna"
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Cubic and rhombohedral Ba4Lu3F17:Er3+ in transparent glass ceramics: Crystallization and upconversion luminescence
Krieke, Guna; Sarakovskis, Anatolijs; Springis, Maris (Elsevier B.V., 2018)Novel Er3+ doped glass ceramics containing Ba4Lu3F17 nanocrystals were successfully prepared by heat treatment of melt-quenched glasses. Highly efficient upconversion luminescence was detected under near-infrared excitation ... -
Electron paramagnetic resonance and photoluminescence investigation of europium local structure in oxyfluoride glass ceramics containing SrF2 nanocrystals
Antuzevics, Andris; Kemere, Meldra; Krieke, Guna; Ignatans, Reinis (Elsevier B.V., 2017)Different compositions of europium doped aluminosilicate oxyfluoride glass ceramics prepared in air atmosphere have been studied by electron paramagnetic resonance (EPR) and optical spectroscopy methods. X-ray diffraction ... -
Eu3+ ion distribution in oxyfluoride glass nanocomposites
Antuzevics, Andris; Krieke, Guna; Pavlovska, Elina; Rogulis, Uldis (Elsevier, 2019)Assessment of activator distribution in lanthanide doped nanocomposites is an important and challenging task. Oxyfluoride glass ceramics have been chosen as a model system to characterize incorporation efficiency of Eu3+ ... -
Low-temperature studies of Cr3+ ions in natural and neutron-irradiated Mg-Al spinel
Mironova-Ulmane, Nina; Popov, Anatoli I.; Krieke, Guna; Antuzevics, Andris; Skvortsova, V.; Elsts, Edgars; Sarakovskis, Anatolijs (American Institute of Physics, 2020)Original results on the EPR and photoluminescence Cr3+ ions in natural magnesium aluminum spinel (MgAl2O4) are presented. The photoluminescence spectra of Cr3+ ions in natural MgAl2O4 have been measured before and after ... -
Multisite formation in gadolinium doped SrF2 nanoparticles
Antuzevics, Andris; Kemere, Meldra; Krieke, Guna (Elsevier B.V., 2018)Gadolinium doped SrF2 nanoparticles have been synthesized by the precipitation method and characterized by site-selective optical spectroscopy and electron paramagnetic resonance (EPR) spectroscopy methods at cryogenic ... -
Novel method of phosphorescent strontium aluminate coating preparation on aluminum
Bite, Ivita; Krieke, Guna; Zolotarjovs, Aleksejs; Laganovska, Katrina; Liepina, Virginija; Smits, Krisjanis; Auzins, Krisjanis; Grigorjeva, Larisa; Millers, Donats; Skuja, Linards (Elsevier Ltd, 2018)This study presents a novel approach to produce phosphorescent coatings on metal surfaces. Strontium aluminates are the most popular modern phosphorescent materials exhibiting long afterglow at room temperature and a broad ... -
Ordering of fluorite-type phases in erbium-doped oxyfluoride glass ceramics
Krieke, Guna; Sarakovskis, Anatolijs; Springis, Maris (Elsevier B.V., 2018)In this study, novel transparent Er3+ doped glass ceramics were prepared from melt-quenched oxyfluoride glasses with general composition of Na2O-NaF-BaF2-YbF3-Al2O3-SiO2. The crystallization of fluorite (BaF2, BaF2-YbF3, ... -
Oxidation State and Local Structure of Chromium Ions in LaOCl
Antuzevics, Andris; Krieke, Guna; Ozols, Haralds; Fedotovs, Andris; Sarakovskis, Anatolijs; Kuzmin, Alexei (MDPI, 2021)LaOCl doped with 0–10 mol% Cr was synthesized by thermal decomposition of chlorides. X-ray diffraction (XRD) analysis revealed that incorporation of chromium results in a decrease of the lattice parameter a and a simultaneous ... -
Phase transitions and upconversion luminescence in oxyfluoride glass ceramics containing Ba4Gd3F17 nanocrystals
Krieke, Guna; Sarakovskis, Anatolijs; Ignatans, Reinis; Gabrusenoks, Jevgenijs (Elsevier B.V., 2017)Novel transparent Er3+ doped oxyfluoride glass-ceramics containing Ba4Gd3F17 nanocrystals were prepared by melt quenching followed by heat treatment of as-prepared glasses. The phase composition and microstructure were ... -
Shortwave Ultraviolet Persistent Luminescence of Sr2MgSi2O7: Pr3+
Antuzevics, Andris; Doke, Guna; Krieke, Guna; Rodionovs, Pavels; Nilova, Dace; Cirulis, Jekabs; Fedotovs, Andris; Rogulis, Uldis (MDPI, 2023)Currently, extensive research activities are devoted to developing persistent phosphors which extend beyond the visible range. In some emerging applications, long-lasting emission of high-energy photons is required; however, ... -
Upconversion luminescence in transparent oxyfluoride glass ceramics containing hexagonal NaErF4
Krieke, Guna; Antuzevics, Andris; Springis, Maris; Rogulis, Uldis (Elsevier, 2019)Transparent oxyfluoride glass ceramics containing hexagonal NaErF4 nanocrystals were synthesized by a heat treatment of a precursor glass obtained by the melt quenching technique. Combined X-ray diffraction (XRD) and ... -
Upconversion luminescence in transparent oxyfluoride glass ceramics containing hexagonal NaErF4
Krieke, Guna; Antuzevics, Andris; Springis, Maris; Rogulis, Uldis (Elsevier B.V., 2019)Transparent oxyfluoride glass ceramics containing hexagonal NaErF4 nanocrystals were synthesized by a heat treatment of a precursor glass obtained by the melt quenching technique. Combined X-ray diffraction (XRD) and ... -
Upconversion luminescence of a transparent glass ceramics with hexagonal Na(Gd,Lu)F4 nanocrystals
Krieke, Guna; Sarakovskis, Anatolijs; Springis, Maris (Elsevier B.V., 2017)Novel Er3+ doped transparent glass ceramics containing hexagonal Na(Gd,Lu)F4 nanocrystals were prepared from oxyfluoride glasses. The distribution of rare earth ions in the crystalline and glassy phase has been analyzed ... -
Upconversion luminescence of Er3 +/Yb3 + and their role in the stabilization of cubic NaLaF4 nanocrystals in transparent oxyfluoride glass ceramics
Krieke, Guna; Sarakovskis, Anatolijs; Springis, Maris (Elsevier B.V., 2018)Novel Er3 + and Yb3 + doped transparent oxyfluoride glass ceramics containing NaLaF4 nanocrystals were prepared from oxyfluoride glasses with general composition of Na2O-NaF-LaF3-Al2O3-SiO2. The crystallization processes, ...