Luminescence Properties and Decay Kinetics of Mn 2+ and Eu 3+ Co-Dopant Ions in MgGa 2 O 4 Ceramics

A. Luchechko gratefully acknowledges a grant from the Institute of Physics PAS for a research visit to the institute, while A.I. Popov has been supported by project LZP-2018/1-0214 from the Latvian Council of Science.The MgGa 2 O 4 ceramics co-doped with Mn 2+ and Eu 3+ ions were synthesized via a higherature solid-state reaction technique. The samples with various Eu 3+ concentrations were characterised using high-resolution photoluminescence (PL) spectroscopy. The PL spectra show weak matrix emission in a blue spectral region with dominant excitation band around 380 nm. Manganese ions are highly excited deeply in UV region and exhibit emission band peaked at 502 nm. The Eu 3+ ions show characteristic f-f excitation and emission lines. The energy transfer between host defects and activator ions was observed. Luminescence decay curves of Mn 2+ and Eu 3+ emission showed complex kinetics with both Eu 3+ -ion concentration and excitation wavelength changes.Latvian Council of Science LZP-2018/1-0214; Latvian–Ukrainian Joint Research Project LV-UA/2016/1,M/.8-2018; project DB/RIDER0117U004443; 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 CAMART

Thermally induced fading of Mn-doped YAP nanoceramic

We study pomax games, a family of combinatorial games which are always integer-valued. Specifically, we study games played on Young diagrams and Boolean lattices. We find a linear algorithm for computing the values of pomax games played on Young diagrams with only two rows. Some of the statements involved in this proof hold also for games on general Young diagrams. For pomax games on Boolean lattices, we introduce the concept of upper and lower games and use that as a tool to study the distribution of possible game values. We prove that games that equal any sufficiently small even integer can always be found, and that the density of distinct game values converges when the game size tends to infinity. Based on computational evidence, we conjecture that if the upper and lower games of some game are identical, then the value of that game is the sum of the upper and lower game.Vi studerar pomaxspel, en familj av heltalsvärda kombinatoriska spel. Mer specifikt studerar vi dessa spel då de spelas på Youngdiagram och Boolska lattis. Vi hittar en linjär algoritm för att beräkna värdet av pomaxspel på Youngdiagram med som mest två rader. Vissa av de ingående resultaten håller även for spel på allmänna Youngdiagram. Gällande pomaxspel pa Boolska lattis introducerar vi koncepten övre och undre spel, och använder detta for att analysera fördelningen av möjliga spelvärden. Vi visar att det alltid finns spel av varje tillräckligt litet jämnt värde, och att densiteten av distinkta spelvärden konvergerar då spelstorleken går mot oändligheten. Baserat på beräkningar förmodar vi att om det övre och undre spelet hörande till något spel ar identiska, så är detta spel lika med summan av det övre och undre spelet

Afterglow, TL and OSL properties of Mn2+-doped ZnGa2O4 phosphor

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 CAMART

Modeling and optimization of the YAG:Yb microchip laser passively Q-switched by YAG:Cr absorber

Based on analytical and numerical solutions of the rate equations system and the heat conductivity equation, the model of the quasi-three-level passively Q-switched YAG:Yb/YAG:Cr microchip laser is developed. The obtained results are used for its optimization, i.e., for the determination of the output mirror reflectivity, the pumping beam radius, the thickness of the absorber and the phototropic centers concentration maximizing the energy in the laser pulse. The influence of the thermal load on the spatial parameters of the laser beam is also determined

The MAS NMR study of solid solutions based on the YAG crystal

An 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) study of nominally pure and Cr-doped yttrium-aluminum garnet (Y3Al5O12 and Y3Al5O12:Cr) crystals is reported. It has been shown that the doping by Cr of the Y3Al5O12 crystals leads to the variation of the occupation by Al atoms both octahedrally and tetrahedrally coordinated sites of the garnet lattice

X-ray excited luminescence of ytterbium containing YAG single crystalline films

Luminescence properties of ytterbium ions in of У₃AI₅О₁₂ (УAG) epitaxial films have been investigated. The influence of growth conditions on the change of activator ions charge state and the luminescence in visible spectral region has been demonstrated. It has been established that emission bands with maxima at 480 and 580 nm are attributed to the 5d-4f transitions of Уb²⁺ ions. The emission bands with maxima at 330 nm and 500 nm correspond to transitions from charge transfer state to ²F₇/₂ and and ²F₅/₂ state of Уb³⁺ ions, respectively.Проведено исследование люминесцентных свойств ионов иттербия в эпитаксиальных пленках У₃AI₅О₁₂ (УAG). Показано влияние условий выращивания на изменение зарядового состояния ионов активатора и его свечения в видимой области спектра. Установлено, что люминесценция в полосах с максимумами при 480 нм и 580 нм в эпитаксиальных пленках УAG:Уb приписывается 5d-4f переходам ионов Уb²⁺. Полосы свечения с максимумами при 330 и 500 нм отвечают переходам из состояния переноса заряда соответственно на уровни ²F₇/₂ и ²F₅/₂ ионов Уb³⁺.Проведено дослiдження люмiнесцентних властивостей iонiв iтербiю в епiтаксiйних плiвках У₃AI₅О₁₂ (УAG). Показано вплив умов вирощування на змiну зарядового стану iонiв активатора та його свiчення у видимiй областi спектра. Встановлено, що люмiнеcценцiя в смугах з максимумами при 480 нм i 580 нм приписується 5d-4f переходам iонiв Уb²⁺. Смуги свiчення з максимумами при 330 i 500 нм вiдповiдають переходам зi стану перенесення заряду вiдповiдно на рiвнi ²F₇/₂ i ²F₅/₂ iонiв Уb³⁺

Optical in situ Study of Reduction/Oxidation Processes in Cr,Mg:YAG Epitaxial Film

The changes of the optical absorption spectra of Cr,Mg:YAG epitaxial film caused by high-temperature redox treatment are investigated by means of in situ spectroscopy. The spectra were registered in the visible and near-IR spectral regions at temperatures up to 1100 K. The kinetics of optical absorption changing were obtained in the temperature range from 936 K to 1091 K and were described by mathematical model connecting the chromium recharging process with oxygen vacancies diffusion. The parameters of the model were determined from the approximations of the experimental kinetics

Structural behaviour of continuous solid solution SmCo₁₋xFexO₃

Phase and structural behaviour in the SmCoO₃-SmFeO₃ pseudobinary system has been investigated at the ambient conditions in a whole concentration range by means of X-ray powder diffraction technique applied laboratory and synchrotron radiation sources. Series of mixed samarium cobaltites-ferrites SmCo₁₋xFexO₃ was obtained by the solid state reaction in air at 1573 K. Formation of a continuous solid solution SmCo₁₋xFexO₃ with orthorhombic perovskite structure (GdFeO₃ type, space group Pbnm) has been revealed. Crystal structure parameters of the mixed samarium cobaltites-ferrites, as well as nominally pure SmCoO₃ and SmFeO₃ have been established by full profile Rietveld refinement. Based on the analysis of structural parameters, an influence of the cation substitution on the deformation of the orthorhombic perovskite structure in the SmCo₁₋xFexO₃ series has been established