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

Synthesis and Structure Characterisation of Micro-and Nanocrystalline Powders of Dy_{1-x}R_xFeO₃ (R = La, Pr, Nd, Sm, Gd)

This work deals with the study of the phase and crystal structure behaviour of new micro- and nanocrystalline ferrites Dy_{1-x}R_xFeO₃ obtained by solid state reactions (R = La, Pr) and sol-gel citrate (R = Nd, Sm, Gd) techniques. It was established that all synthesized samples adopt orthorhombic perovskite structure isotypic with GdFeO₃. Unit cell dimensions and atomic coordinates of the mixed rare earth ferrites derived by full profile Rietveld refinement technique agree well with the data of the "pure" DyFeO₃ and RFeO₃ compounds, thus proving formation of continuous solid solutions Dy_{1-x}R_xFeO₃ in the DyFeO₃-RFeO₃ systems (R = La, Pr, Nd, Sm, Gd). Peculiarity of the Dy_{1-x}La_xFeO₃ series is the lattice parameters crossover and formation of dimensionally tetragonal structure at x ≈0.97

Optical Properties of GGG Epitaxial Films Grown from PbO-B₂O₃-V₂O₅ Flux

The paper reports a growth of the high-quality Gd₃Ga₅O₁₂ (GGG) homoepitaxial films by the liquid phase epitaxy technique using the PbO-B₂O₃ and PbO-B₂O₃-V₂O₅ fluxes. The influence of the flux composition containing V₂O₅ as well as the growth temperature is discussed basing on the optical absorption and the electron probe micro analysis results

Optical Properties of GGG Epitaxial Films Grown from PbO-B 2

The paper reports a growth of the high-quality Gd₃Ga₅O₁₂ (GGG) homoepitaxial films by the liquid phase epitaxy technique using the PbO-B₂O₃ and PbO-B₂O₃-V₂O₅ fluxes. The influence of the flux composition containing V₂O₅ as well as the growth temperature is discussed basing on the optical absorption and the electron probe micro analysis results

Effect of Lutetium Co-Doping on the Main Dosimetric Peak of YAP:Mn²⁺ Thermoluminescent Detectors

An effect of lutetium co-doping on photoluminescent and thermoluminescent properties of the Mn²⁺-doped (Lu-Y)AP crystals (with Lu content from 0 to 20% with respect to Y) grown by the Czochralski technique has been studied. It was found that the maximum of the thermoluminescent peak at 200°C is shifted towards higher temperatures at Lu content more than 5%. At the same time the position of the second thermoluminescent peak near 350°C remains unchanged. The observed changes in the thermoluminescent peak position are discussed in terms of the point defects of the material

Photoluminescence and thermoluminescence of the oxygen-deficient YAG, YAP, and YAM phosphors

Photoluminescence and thermoluminescence of the oxygen-deficient Y₃Al₅O₁₂ (YAG), YAlO₃ (YAP) and Y₄Al₂O₉ (YAM) ceramics has been studied. Corresponding ceramic samples prepared by the same way however in oxidizing conditions (in air) were studied for comparison. The observed luminescent properties of the materials are related to the F-type centers created on the basis of oxygen vacancies, antisite (Y_{Al}) defects and uncontrolled Tb³⁺ impurity ions

Investigation of Co Ions Diffusion in Gd 3

Spatial changes of properties of Gd₃Ga₅O₁₂ (GGG) single crystals caused by diffusion of cobalt ions during high-temperature annealing (1200°C, 24 h) in Co₃O₄ powder are investigated. The registration of these changes was carried out by optical spectrophotometry, microscopy and micro-Raman scattering methods. Changes in structure of near-surface layers of the crystal were investigated by X-ray diffraction technique. It was shown that the additional absorption induced by annealing is related to intra-center optical transitions in Co²⁺ ions, which occupy tetrahedral positions in the garnet structure at the distances of 250-500 μm from the crystal surface. The dependence of induced absorption with depth has got a non-monotonous character with a maximum at 400 μm. A comparison of the results obtained by different methods allows to suppose that the thermal treatment of GGG in the presence of cobalt ions leads to formation of the structurally and chemically non-uniform layer with a width about 500 μm

Photoluminescence and Thermoluminescence of the Oxygen-Deficient YAG, YAP, and YAM Phosphors

Photoluminescence and thermoluminescence of the oxygen-deficient Y₃Al₅O₁₂ (YAG), YAlO₃ (YAP) and Y₄Al₂O₉ (YAM) ceramics has been studied. Corresponding ceramic samples prepared by the same way however in oxidizing conditions (in air) were studied for comparison. The observed luminescent properties of the materials are related to the F-type centers created on the basis of oxygen vacancies, antisite (Y_{Al}) defects and uncontrolled Tb³⁺ impurity ions

Investigation of Co Ions Diffusion in Gd₃Ga₅O₁₂ Single Crystals

Spatial changes of properties of Gd₃Ga₅O₁₂ (GGG) single crystals caused by diffusion of cobalt ions during high-temperature annealing (1200°C, 24 h) in Co₃O₄ powder are investigated. The registration of these changes was carried out by optical spectrophotometry, microscopy and micro-Raman scattering methods. Changes in structure of near-surface layers of the crystal were investigated by X-ray diffraction technique. It was shown that the additional absorption induced by annealing is related to intra-center optical transitions in Co²⁺ ions, which occupy tetrahedral positions in the garnet structure at the distances of 250-500 μm from the crystal surface. The dependence of induced absorption with depth has got a non-monotonous character with a maximum at 400 μm. A comparison of the results obtained by different methods allows to suppose that the thermal treatment of GGG in the presence of cobalt ions leads to formation of the structurally and chemically non-uniform layer with a width about 500 μm