Zolotarjovs

Radioluminescence, thermoluminescence and dosimetric properties of ZnO ceramics

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Larisa Grigorjeva, Aleksejs Zolotarjovs, Sergej Yu Sokovnin, Donats Millers, Krisjanis Smits, Vladislav G. Il`ves

Two types of ZnO ceramics were fabricated and characterized by XRD, SEM methods. The radioluminescence spectra were measured within the 300–550 K range. The defect luminescence band peaking at ~2.35 eV is the dominant one in radioluminescence spectra in both of the fabricated ceramics. The thermostimulated luminescence (TSL) glow-curves were measured after X-ray irradiation at 300 K. It was concluded that the complex overlapping peak within the 320–450 K temperature range consists of two components (~360–375 K and 400–420 K). The ratio of component intensities differs in both ceramics. The positions of high temperature TSL components (480–520 K) also differ in both samples; therefore not only sintering conditions but also the properties of the initial powder are very important for characteristics of TSL. A linear dependence of peak intensity on irradiation dose was observed up to ~3 kGy for ceramic 1 and up to 9 kGy for ceramic 2.

cer_int_2017_img

Ceramics International

DOI: 10.1016/j.ceramint.2017.02.016

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Effect of Mg2+ ions co-doping on luminescence and defects formation processes in Gd3(Ga,Al)5O12:Ce single crystals

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V. Babin , P. Bohacek , L. Grigorjeva , M. Kucera , M. Nikl , S. Zazubovich , A. Zolotarjovs
Photo- and radioluminescence and thermally stimulated luminescence characteristics of Ce3+ – doped
and Ce3+, Mg2+ co-doped Gd3(Ga,Al)5O12 (GAGG) single crystals of similar composition are investigated in the 9-500 K temperature range. The Ce3+ – related luminescence spectra and the photoluminescence decay kinetics in these crystals are found to be similar. Under photoexcitation in the Ce3+ – and Gd3+ – related absorption bands, no prominent rise of the photoluminescence intensity in time is observed neither in GAGG:Ce,Mg nor in GAGG:Ce crystals. The afterglow is strongly reduced in GAGG:Ce,Mg as compared to GAGG:Ce, and the afterglow decay kinetics is much faster. Co-doping with Mg2+ results in a drastic decrease of the thermally stimulated luminescence (TSL) intensity in the whole investigated temperature range and in the appearance of a new complex Mg2+ – related TSL glow curve peak around 285 K. After irradiation in the Ce3+ – related 3.6 eV absorption band, the TSL intensity in GAGG:Ce,Mg is found to be comparable with that in the GAGG:Ce epitaxial film of similar composition. The Mg2+ – induced changes in the concentration, origin and structure of the crystal lattice defects and their influence on the scintillation characteristics of GAGG:Ce,Mg are discussed.

2017 gagg paper

Optical Materials 66 (2017) 48-58

DOI: 10.1016/j.optmat.2017.01.039

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Luminescent PEO Coatings on Aluminum

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Aleksejs Zolotarjovs, Krisjanis Smits, Anete Krumina, DonatsMillers, and Larisa Grigorjeva

Results show the possibilities of pore filling approach to modify alumina coatings with various materialspeo-raksta-bilde in order to enhance coating optical (or other) properties and develop new functional materials; as well as demonstrate novel alumina phase transition detection approach. Luminescent PEO coatings were
produced on aluminum surface using pore-filling method. Three stage process was developed to modify alumina coating in order to enhance its luminescent properties. Eu3+ recharging to Eu2+ followed by significant (up to 10 times) total luminescence intensity increase was observed, Eu ion presence evaluated in final coating by measuring fast decay kinetics. Structure of obtained coatings was analyzed using XRD and FTIR spectroscopy indicating presence of η-alumina phase.

ECS Journal of Solid State Science and Technology, 5 (9) R150-R153 (2016)

DOI: 10.1149/2.0401609jss

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Effect of Point Defects on Luminescence Characteristics of ZnO Ceramics

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P. A. Rodnyi, K. A. Chernenko, A. Zolotarjovs, L. Grigorjeva,
E. I. Gorokhova, and I. D. Venevtsev

Abstract—Photo- and thermally stimulated luminescence of ZnO ceramics are produced by uniaxial hot pressing. The luminescence spectra of ceramics contain a wide band with a maximum at 500 nm, for which oxygen vacancies VO are responsible, and a narrow band with a maximum at 385 nm, which is of exciton nature. It follows from luminescence excitation spectra that the exciton energy is transferred to luminescence centers in ZnO. An analysis of the thermally stimulated luminescence curves allowed detection of a set of discrete levels of point defects with activation energies of 25, 45, 510, 590 meV, and defects with continuous energy distributions in the range of 50–100 meV. The parameters of some of the detected defects are characteristic of a lithium impurity and hydrogen centers. The photoluminescence kinetics are studied in a wide temperature range.
DOI: 10.1134/S1063783416100309

ISSN 1063-7834,

Physics of the Solid State, 2016, Vol. 58, No. 10, pp. 2055–2061.

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Rare earth doped glass–ceramics containing NaLaF4 nanocrystals

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E. Elsts , G. Krieke, U. Rogulis, K. Smits, A. Zolotarjovs, J. Jansons, A. Sarakovskis, K. Kundzins

Oxyfluoride glasses 16Na2O–9NaF–5LaF3–7Al2O3–63SiO2 (mol%) activated with 3% terbium, dysprosium,
praseodymium and neodymium fluorides have been prepared and studied by differential thermal analysis,
cathodoluminescence, X-ray induced luminescence, X-ray diffraction, scanning electron microscopy
and energy dispersive X-ray spectroscopy. We found out that the presence of crystalline phase enhances
the X-ray induced luminescence intensity. X-ray induced luminescence is the most intense for the sample
activated with terbium and treated at 700 C, whereas the praseodymium and neodymium activated
samples have the fastest decay times.

Optical Materials xxx (2016) xxx–xxx

doi: 10.1016/j.optmat.2016.01.005

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Gas sensitive luminescence of ZnO coatings obtained by plazmaelectrolytic oxidation

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L. Grigorjeva, D. Millers, K. Smits, A. Zolotarjovs

The ZnO coatings on Zn substrate were obtained using plasma electrolytic oxidation method. The XRDand SEM methods were used for structural and morphological characterization of obtained coatings. Theluminescence of ZnO coatings were studied and compared with luminescence characteristics of ZnO sin-gle crystal. It is shown that luminescence intensity in ZnO defect band depends on oxygen concentrationin ambient atmosphere. The effect is of interest for oxygen sensing based on ZnO coating luminescence

Sensors and Actuators A 234 (2015) 290–293

doi:10.1016/j.sna.2015.09.018

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Luminescence of Eu ion in alumina prepared by plasma electrolyticoxidation

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Krisjanis Smitsa, Donats Millers, Aleksejs Zolotarjovs,Reinis Drunka, Martins Vanks

Eu ion luminescence in aluminium oxide nanocrystals and layers prepared by plasma electrolytic oxida-tion (PEO) are investigated in this study. The Eu ion in PEO coatings has intense luminescence allowingsuch material to be used for preparation of various phosphor materials. In this study, Eu ion doped coatingswere prepared with two methods: anodization and pulsed bipolar plasma electrolytic oxidation. Also,for comparative studies, alumina nanocrystals with the same amount of Eu ions were prepared using SolGel and molten salts methods.Obtained Eu-doped coatings were studied using luminescence methods. Typical Eu ion luminescencebands were observed, however intensity and spectral distribution differs drastically depending on prepa-ration method and parameters used, therefore the Eu ion luminescence could be used as coating qualityluminescent probe. Additionally, the possibility to incorporate the Eu ions in trivalent or divalent stateexhibiting bright red and blue luminescence accordingly was demonstrated by using different oxidationparameters. Moreover, comparison measurements between powder samples and coatings were made.

Applied Surface Science 337 (2015) 166–171

doi:10.1016/j.apsusc.2015.02.085

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Thermally stimulated luminescence of undoped and Ce3+-doped Gd2SiO5 and (Lu,Gd)2SiO5 single crystals

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V. Bondar, L. Grigorjeva, T. Kärner, O. Sidletskiy,
K. Smits, S. Zazubovich, A. Zolotarjovs

Thermally stimulated luminescence (TSL) characteristics (TSL glow curves and TSL
spectra) are investigated in the 4-520 K temperature range for the X-ray irradiated at 4 K, 8
K, or 80 K single crystals of gadolinium and lutetium-gadolinium oxyorthosilicates. The
nominally undoped Gd2SiO5 and (Lu,Gd)2SiO5 crystals, containing traces of Ce3+, Tb3+, and
Eu3+ ions, and Ce3+-doped Gd2SiO5 and (Lu,Gd)2SiO5 crystals are studied. For the first time,
the TSL glow curves of these materials are measured separately for the electron (intrinsic,
Ce3+- or Tb3+-related) and hole (Eu3+-related) recombination luminescence, and the TSL glow
curve peaks, arising from thermal decay of various electron and hole centers, are identified.
The origin of the traps related to the TSL peaks is discussed, and thermal stability parameters
of the electron and hole traps are calculated.

Journal of Luminescence

DOI:10.1016/j.jlumin.2014.11.034

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Studies of radiation defects in cerium, europium and terbium activated oxyfluoride glasses and glass ceramics

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E. Elsts , U. Rogulis, K. Bulindzs, K. Smits, A. Zolotarjovs, L. Trinkler, K. Kundzins

Terbium, cerium and europium activated oxyfluoride glasses and glass ceramics have been studied by
thermally stimulated luminescence (TSL) and optical absorption techniques after the X-ray irradiation.
A creation of colour centres in oxyfluoride glass matrix and TSL peaks depending on the activator type
were observed. LaF3 and rare earth activators were analysed by SEM–EDS.

Optical Materials 41 (2015) 90–93

DOI: 10.1016/j.optmat.2014.10.042

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TSL and fractional glow study of Ge-doped α-quartz.

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A. Zolatarjovs, A.N. Trukhin, K. Smits, D. Millers

Abstract. Crystalline α-quartz doped with 0.1wt% and 0.9wt% germanium was studied using
TSL and FGT equipment. Sample was chosen because previously it is known that Ge in quartz
is efficient trap for electrons, therefore it could be used for detection of hypothetic self-trapped
hole in α-quartz. However previous investigations of ODMR and TSL shows that in α-quartz
the hole is still mobile and trapping occurs only on defect states. The activation energies for
both TSL peaks are found by fractional glow and Hoogenstraaten method. The TSL
distribution changes depending on Ge concentration and also on irradiation type. The TSL
peaks below 70K in quartz doped with Ge could belong to hole trapped on Ge.

IOP Conference Series: Materials Science and Engineering 49 (2013) 012056

doi:10.1088/1757-899X/49/1/012056

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