Suchergebnisse

The authors are grateful to Dr. Andris Fedotovs for photography of the samples. This research is funded by the Latvian Council of Science, project "Novel transparent nanocomposite oxyfluoride materials for optical applications", project No. LZP-2018/1-0335. ; 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+ ions in CaF2 nanocrystals using a combination of X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) techniques. Lattice constant changes induced by size mismatch of Eu3+ and Ca2+ ions have been used to evaluate Eu3+ content in CaF2. The distortion of CaF2 lattice due to incorporation of europium ions can be detected from EPR investigations via Gd3+ paramagnetic probe spectra. It is shown that ratio of different symmetry CaF2:Gd3+ centres and linewidth of EPR transitions can be used to monitor europium content in the crystalline phase of glass ceramics. --- / / / --- This is the preprint version of the following article: A. Antuzevics, G. Krieke, E. Pavlovska, U. Rogulis, Eu3+ ion distribution in oxyfluoride glass nanocomposites, Journal of Non-Crystalline Solids, 522, 119548 (2019), DOI https://doi.org/10.1016/j.jnoncrysol.2019.119548, which has been published in final form at https://www.sciencedirect.com/science/article/abs/pii/S0022309319304193. This article may be used for non-commercial purposes in accordance with Elsevier Terms and Conditions for Sharing and Self-Archiving. This work is licensed under a CC BY-NC-ND 4.0 license. ; Latvian Council of Science LZP-2018/1-0335; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART².

The authors wish to express gratitude to K. Smits for TEM measurements. This research is funded by the Latvian Council of Science, project "Novel transparent nanocomposite oxyfluoride materials for optical applications", project No. LZP-2018/1-0335. GK wishes to expresses gratitude to Arnis Riekstins "MikroTik" donation. Donations are administered by the University of Latvia Foundation. © 2019. This work is licensed under a CC BY-NC-ND 4.0 license. ; 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 transmission electron microscopy (TEM) analysis revealed the formation of single phase nanocrystals in the glass ceramics. The enhancement of intensity and spectral change of upconversion luminescence (UCL) confirmed the presence of Er3+ ions in the crystalline phase of the glass ceramics. Dominant energy transfer processes were identified using the rate equation formalism. Time-resolved site-selective spectroscopy studies at low temperatures were employed to elucidate the local structure of Er3+ ions in the glass ceramics and microcrystalline NaErF4. The origin of multi-site formation in hexagonal NaErF4 lattice is discussed. --- / / / --- This is the preprint of the following article: Guna Krieke; Andris Antuzevics, Maris Springis, Uldis Rogulis, Upconversion luminescence in transparent oxyfluoride glass ceramics containing hexagonal NaErF4, Journal of Alloys and Compounds Volume 798 (2019), which has been published at https://www.sciencedirect.com/science/article/abs/pii/S0925346717304731. This article may be used for non-commercial purposes in accordance with Elsevier Terms and Conditions for Sharing and Self-Archiving. © 2019. This work is licensed under a CC BY-NC-ND 4.0 license. ; Latvian Council of Science LZP-2018/1-0335; University of Latvia Foundation; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART².

The advances of EPR spectroscopy for the detection of activators as well as determining their local structure in the crystalline phase of glass ceramics is considered. The feasibility of d-element (Mn2+, Cu2+) and f-element (Gd3+, Eu2+) ion probes for the investigation of glass ceramics is discussed. In the case of Mn2+, the information is obtained from the EPR spectrum superhyperfine structure, for Gd3+ and Eu2+ probes – from the EPR spectrum fine structure, whereas for Cu2+ ions the changes in the EPR spectrum shape could be useful. The examples of EPR spectra of the above-mentioned probes in oxyfluoride glass ceramics are illustrated. --- / / / --- This is the preprint version of the following article: A. Antuzevics, U. Rogulis, A. Fedotovs, A.I. Popov, Crystalline phase detection in glass ceramics by EPR spectroscopy, Low Temperature Physics 44, 341 (2018), which has been published in final form at https://aip.scitation.org/doi/abs/10.1063/1.5030462?journalCode=ltp by AIP Publishing. This article may be used for non-commercial purposes in accordance with AIP Publishing Terms and Conditions for Sharing and Self-Archiving. ; The authors thank Meldra Kemere and Dr. Edgars Elsts for sample synthesis and Reinis Ignatans for XRD measurements. Financial support of Latvian-Ukrainian Joint Research Project No. LV-UA/2016/1 is acknowledged. Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

Electron paramagnetic resonance (EPR), magnetic circular dichroism (MCD) and EPR detected via MCD (MCD-EPR) investigations have been performed on rare-earth activated oxyfluoride glasses and glass-ceramics. Er3+, Gd3+, and Mn2+ activators in oxyfluoride glass-ceramics show paramagnetic MCD behaviour and the MCD-EPR has been detected. The results of the MCD-EPR measurements for the Er-doped oxyfluoride glass-ceramics showed that Er3+ ions in the CaF2 crystallites in these ceramics embed only in the cubic symmetry environment, similarly to the previous observations of cubic Gd3+ centres in the glass-ceramics containing CaF2. Finally, the correlation of optics and paramagnetic centres is discussed for Mn-doped YAlO3 ceramics. ; Latvian-Ukrainian Joint Research Project (No LV-UA/2016/1 in Latvia and No M/78-2016 in Ukraine); Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

This research is funded by the Latvian Council of Science , project "Novel transparent nanocomposite oxyfluoride materials for optical applications", project No. LZP-2018/1–0335 . The crystal growth research was funded by the CNPq (Brazil), project NO 421581/2016–6 . ; Recombination luminescence (RL) and RL-detected electron paramagnetic resonance (RL-EPR) in BaY2F8 single crystal has been investigated after irradiation with X-rays at low temperature. The recombination process, which lasts for several hours at 4 K, results in several broad bands in the RL spectrum. RL-EPR spectra show pronounced angular dependences on crystal orientation relative to external magnetic field. Based on the determined spin-Hamiltonian parameter values the recombination centres have been proposed to be F-type electron and self-trapped hole (VK) centres ; Latvian Council of Science LZP-2018/1–0335; CNPq 421581/2016–6; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

This project has received funding from European Social Fund (project No 09.3.3-LMT-K-712-19-0069) under grant agreement with the Research Council of Lithuania (LMTLT). Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART². The World Federation of Scientists is highly acknowledged for the National Scholarship to AZ. © 2021. This work is licensed under a CC BY-NC-ND 4.0 license. ; In this work, a series of Mn2+-doped α-tricalcium phosphate (α-TCP) powders was synthesized by wet co-precipitation method followed by high-temperature annealing and thermal quenching. It was shown that Mn2+-doped α-TCP polymorph can be successfully synthesized with a doping level up to 1 mol%. All Mn-doped samples exhibited a broadband emission in the range from 525 to 825 nm with a maximum centered at around 630 nm. The highest emission intensity was observed for the sample with the highest content of Mn. The crystal structure and purity were evaluated by powder X-ray diffraction (XRD), Fourier-transform infrared (FTIR) and electron paramagnetic resonance (EPR) spectroscopies. Scanning electron microscopy (SEM) was used to investigate the morphological features of the synthesized products. Optical properties were investigated by means of photoluminescence measurements. Excitation spectra, emission spectra and decay curves of the samples were studied. Temperature-dependent photoluminescence measurements were performed as well. --- / / / --- This is the preprint version of the following article: Lauryna Sinusaite, Andris Antuzevics, Anatoli I. Popov, Uldis Rogulis, Martynas Misevicius, Arturas Katelnikovas, Aivaras Kareiva, Aleksej Zarkov, Synthesis and luminescent properties of Mn-doped alpha-tricalcium phosphate, Ceramics International 47 (4) (2021), https://doi.org/10.1016/j.ceramint.2020.10.114, which has been published in final form at https://www.sciencedirect.com/science/article/pii/S0272884220331540. This article may be used for non-commercial purposes in accordance with Elsevier Terms and Conditions for Sharing and Self-Archiving. This work is licensed under a CC BY-NC-ND 4.0 license. ; European Social Fund 09.3.3-LMT-K-712-19-0069; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART².

The work was supported by Latvian Research Council via LZP-2018/1–0214 research project as well as the Latvian-Ukrainian Joint Research Project (LV-UA/2016/1 in Latvia and M/8-2018 (No. 0118U001672) in Ukraine), and by the NATO SfP Project G4649. The work was also partially supported by the Polish National Science Center (project 2018/31/B/ST8/00774). A. Luchechko gratefully acknowledges a grant from Institute of Physics PAS for a research visit to the Institute. ; Zinc gallate (ZnGa2O4) spinel ceramics doped with Mn2+ ions was prepared by a solid-state reaction at 1200 °C in air. Manganese concentration was equal to 0.05 mol.% of MnO with respect to ZnO. Ceramics produced in this way show an efficient green emission at about 505 nm under UV or X-ray excitations, which is caused by Mn2+ ions. This green emission is observed also as a relatively long afterglow (visible to the naked eye in the dark for about one hour) after switching-off the X-ray excitation. Time profiles of the beginning of glow and afterglow have been studied together with thermally stimulated (TSL) and optically stimulated (OSL) luminescence. Experimental results demonstrate a presence of few types of shallow and deep traps responsible for the observed afterglow and TSL/OSL emission of the material. The possibility of pulsed optical stimulation and time-resolved OSL characteristics of ZnGa2 O4: Mn2+ has been reported for the first time. The presented results suggest the ZnGa2O4: Mn2+ spinel as a promising material for further fundamental research and possibility of application as a green long-lasting phosphor or storage phosphor for TSL/OSL radiation dosimetry. ; North Atlantic Treaty Organization G4649; Polish National Science Center project 2018/31/B/ST8/00774; 0118U001672,LV-UA/2016/1,LZP-2018/1–0214; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²