O. Chukova

Comparable Structural and Luminescent Characterization of the La1-xEuxVO4 Solid Solutions Synthesized by Solid State and Co-Precipitation Methods

Luminescence properties of the two series of the La1-xEuxVO4 (x ranges from to 0.3) solid solutions synthesized by the solid state and co-precipitation methods were investigated.. Luminescence spectra of the investigated samples consist of narrow spectral lines caused by inner f - f electron transitions in the impurity Eu3+ ions. Excitation spectra consist of three main bands those correspond to different types of transitions in the investigated matrices. There are O - Eu3+ charge transfer transitions, band-to-band transitions in the matrix of the vanadate compounds and electron transitions in the VO43- vanadate anion. Dependences of the structure and luminescence properties on rate compositions and method of synthesis were studied. Origins of the observed differences between luminescence characteristics of the samples obtained by two different methods are discussed.

Study of Temperature Behavior of Luminescence Emission of LaVO4 and La1-xEuxVO4 Powders

The La1‑xEuxVO4 powders were synthesized by co-precipitation method. Emission spectra of the LaEuVO4 and La1‑xEuxVO4 powders consist of wide non-structural bands of the matrix emission and narrow spectral lines caused by inner f-f electron transitions in the Eu3+ ions, respectively. The both types of emission were studied within 8 – 300 K temperature range. Decomposition of spectra of the wide matrix emission on three bands has been carried out and temperature dependencies for each band were studied. Temperature behavior of the Eu3+ emission was investigated for lines assigned to different Eu3+ centres. Obtained dependencies are analyzed and discussed using proposed schemes of transitions in the VO43- groups and structure of the nearest surrounding of the Eu3+ emission centres.

Effect of X-Rays and Power Laser Irradiation on the Complex Emission Centers in Dielectric Crystals

Irradiation effects on emission centers were studied with photo and X-ray luminescence investigations of alkali chromate crystals. The X-rays and powerful laser irradiations were used for this investigation. The irradiation effects were found to depend on a type and structure of emission centers. In the alkali Chromate crystals complex emission centers of a molecular type are formed by two weight centers: the Chromate oxyanion and the defect. The bond between weight centers can be broken under irradiation action. As established in our experiment, some types of the emission centers can decay or transform into other types under action of irradiation.

Synthesis and structure features of the Ca 1−2x Ce 2x Mo 1−x Ge x O 4 (0 ≤ x≤ 0.2) compounds

The Ca<inf>1−2x</inf>Ce<inf>2x</inf>Mo<inf>1−x</inf>Ge<inf>x</inf>O<inf>4</inf> (0 ≤ × ≤ 0.2) micro/nanosized powders were prepared by aqueous nitrate-tartrate sol-gel synthesis. The obtained samples were characterized by XRD analysis, SEM microscopy, and IR spectroscopy. It was shown, that increase of cerium concentration in the series of compounds does not lead to obvious changes in their crystal structure, but changes of unit cell lattice parameters was fixed. According to SEM analysis, particles of investigation molibdates have diameter 100–500 nm. Luminescence properties of the synthesized powders were studied. The photoluminescence spectra contain wide bands of matrix emission and narrow lines caused by f-f transitions in the RE³⁺ ions.

Study of effects of rare earth impurities on structure of matrix emission of the lead tungstate crystals

The paper reports study of complex structure of matrix emission of undoped and RE-doped PbWO4 crystals. Decomposition of the spectra shows contributions of five components at 410, 485, 520, 565, 635 nm in emission of all the investigated samples. Their relative contributions depend on RE doping. Observed effects of RE doping are the same for the crystals with different RE impurities. Structures of luminescent centres are discussed taking into account studied effects of the impurity RE ions on spectral characteristics of the matrix emission.

Temperature behavior of matrix and impurity emission of La 1−x Eu x VO 4 powders synthesized by co-precipitation method

The La_1-xEu_xVO₄ powders were synthesized by co-precipitation method. Luminescence spectra of the investigated samples consist of wide non-structural bands of the matrix emission and narrow spectral lines caused by inner f-f electron transitions in the impurity Eu³⁺ ions. The both types of emission were studied within 10 - 300 K temperature range. Obtained dependencies are discussed using proposed models for matrix emission and structure of the nearest surrounding of the Eu³⁺ centers.

Spectroscopic investigation of sodium titanium orthophospates wide band red luminescence

The NaTi2(P04)3 crystals were synthesised and their crystal structure and luminescence properties were investigated. Two luminescence bands in green-orange and red spectral regions have been observed. Properties ofthe red emission of the NaTi2(P04)3 crystals were investigated. Cumulative spectral data and their analysis have allowed to assign the red band emission to luminescence ofthe Ti3+ ions, those are formed in the NaTi2(P04)3 crystals during growth.

Synthesis and characterization of sodium titanium orthophosphates with wide band red luminescence

Crystalline samples of the NaTi/sub 2/(PO/sub 4/)/sub 3/ phosphates were synthesized from a melt of oxide composition. Luminescence and excitation spectra were obtained at 4.2, 77 and 300 K temperatures of the samples. Luminescence intensity of the first band essentially decreases with temperature increasing. The red band can be excited in various spectral regions. In the synthesized samples, the Ti/sup 3+/ ions can be formed under the process of high-temperature synthesis and transition from melt into solid state at cooling.