Ya. Zhydachevskii

Photoluminescence studies of Mn4+ ions in YAlO3 crystals at ambient and high pressure

Detailed investigations of the photoluminescence properties of Mn4+ (3d3) ions in YAlO3 have been performed in the temperature range 10–600 K. The luminescence of Mn4+ ions due to the transition consists of two zero-phonon lines (R lines) at 691.3 and 692.7 nm, which became visible only at low temperature, and their vibronic sidebands that cover the range of 660–740 nm. The thermal quenching of the luminescence intensity due to the non-radiative decay occurs at temperatures above 420 K. The temperature dependence of the luminescence decay time shows a quasi-linear decrease from τ = 4.9 to 1.6 ms in the temperature range from 90 to 420 K (with a temperature coefficient −0.01 ms K−1) that makes YAlO3:Mn a potentially good phosphor for a fibre optic fluorescence thermometer in this temperature range. The high-pressure low-temperature luminescence measurements in a diamond-anvil cell reveal similar pressure coefficients for Mn4+ and Cr3+ dopant ions in YAlO3, equal to 1.16 cm−1 kbar−1 and 1.08 cm−1 kbar−1, respectively.

Structural and spectroscopic properties of Mn-doped YAlO3 ceramics

We report results on structural and optical spectroscopic properties of Mn-doped YAlO3 (YAP) ceramics prepared by a solid-state reaction method starting from nanocrystalline oxides. A series of ceramic samples with different Mn concentrations and different Y2O3–Al2O3 compositions have been studied by means of x-ray powder diffraction, scanning electron microscopy, photoluminescence and thermoluminescence measurements. Peculiarities of YAP phase formation and incorporation of manganese ions into the host are discussed. The possible application of Mn-doped YAP ceramics as thermoluminescent screens for visualization of local heating of various origin, including a heating caused by infrared laser light, has been demonstrated.

Optical observation of the recharging processes of manganese ions in YAlO3:Mn crystals under radiation and thermal treatment

Mn-doped YAlO3 crystals have been characterized by means of optical absorption, photoluminescence, x-ray luminescence and thermoluminescence measurements. The influence of after-growth high-temperature thermal treatments of the crystals in oxidizing and reducing atmosphere as well as the effect of co-doping with Si4+ on the optical properties of the crystals have been studied. The recharging processes of manganese ions involving Mn3+, Mn4+ and Mn5+ ions in octahedral (Al) positions, which take place under ionizing irradiation and thermal treatments, have been studied.

In situ investigation of optical absorption changes in LiNbO3 during reducing/oxidizing high-temperature treatments

This paper presents experimental results of an in situ investigation of optical absorption of congruent lithium niobate during reducing (95% Ar + 5% H 2 ) and oxidizing (O 2 ) high-temperature treatments in the temperature range from 20 to 800°C. The absorption spectra measured at in situ conditions at high temperatures in reducing/oxidizing atmospheres as well as the kinetics recorded at fixed wavelength during rapid replacement of gas atmospheres have been analysed. The origin of the changes in optical absorption caused by the redox treatments is discussed in terms of hydrogen and oxygen ion diffusion and the point defect structure of the material.

Growth and properties of YAlO3:Tm single crystals for 2-μm laser operation

Large YAlO3 single crystals doped with thulium (B4 at%) were grown by the Czochralski method. The crystal and twin structures as well as optical and lasing properties of the crystals were investigated. r 2002 Elsevier Science B.V. All rights reserved.

Optical and Luminescence Properties of YAlO3 -Tm Crystals

The results on optical absorption, photoluminescence and thermoluminescence of YAP-Tm crystals of 1 at.% and 4 at.% of Tm are presented as well as influence ofUV-, γ-radiation and thermal treatments on optical and luminescence properties of the crystals. The blue-green luminescence of defect centers was observed in YAP-Tm crystals at Ar + -laser excitation. The possibility of energy transfer processes between defect centers and Tm 3+ ions was shown.

Radiation displacement defect formation in some complex oxide crystals

The work is devoted to an analysis of the formation processes of radiation displacement defects (RDDs) and color centers (CCs) under irradiation of complex oxide crystals. The results of the displacement process simulation as well as the analysis of the RDDs and CCs accumulation kinetics in some complex oxide crystals are presented. New experimental results on additional absorption spectra induced by neutron irradiation of LiNbO3 (LNO) crystals doped with Fe and Cr and YAlO3 (YAP) crystals doped with Nd and Er as well are presented. Dose dependencies are compared and their peculiarities are discussed. ” 2000 Elsevier Science B.V. All rights reserved.

Crystal structure and optical spectroscopy of CaGdAlO4:Er single crystal

Abstract The structure of CaGdAlO 4 single crystal doped with Er has been refined by the Rietveld method using X-ray powder data. The crystal structure belongs to the tetragonal K 2 NiF 4 type structure (space group I4/mmm , Z =4, a =3.65855(6) A, c =11.9787(3) A). Green and blue upconversion emissions from Er 3+ in CaGdAlO 4 at 550 nm, 440 nm and 407 nm due to the 4 S 3/2 → 4 I 15/2 , 4 F 3/2 → 4 I 15/2 and 2 H 9/2 → 4 I 15/2 transitions, respectively, under near-infrared (800 nm) light pumping have been observed.

Thermoluminescent properties of Mn-doped YAP ceramics

The work is devoted to synthesis of Mn-doped YAlO3 (YAP) ceramics by common solid-state reaction and their characterization by photoluminescence and thermoluminescence techniques. An impact of the synthesis conditions on the thermoluminescence (TL) efficiency of the ceramics is analyzed from the point of view of possible application of the material for TL dosimetry of ionizing radiation.

Thermal changes of the crystal structure and the influence of thermo-chemical annealing on the optical properties of YbAlO3 crystals

The paper presents experimental results of investigations on the influence of temperature and thermo-chemical annealing on the structural and optical properties of YbAlO(3) crystals. Thermal behaviour of the crystal structure has been studied in the temperature range of 19-1173 K by means of in situ high-resolution x-ray powder diffraction using synchrotron radiation. Lattice expansion of YbAlO(3) displays a strongly anisotropic character: the relative expansion along the b direction is about two times smaller than that along the a and c axes. The influence of thermo-chemical annealing in oxidizing and reducing atmospheres has been studied by means of in situ optical spectroscopy. The increase of the absorption in the range of 300-600 nm during annealing in an oxidizing atmosphere as well as its bleaching during reduction has been observed in the temperature range 700-1000 K. The oxidation and reduction kinetics have been analysed by means of mathematical models taking into account diffusion and the quasi-chemical reaction of the defect centres.