CARAT Scientific Research Company

L'viv, Ukraine

CARAT Scientific Research Company

L'viv, Ukraine
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Yatsenko A.V.,Vernadsky Crimean Federal University | Pritulenko A.S.,Vernadsky Crimean Federal University | Yagupov S.V.,Vernadsky Crimean Federal University | Sugak D.Y.,Lviv Polytechnic | And 2 more authors.
Technical Physics | Year: 2017

The instability of the electrical properties of lithium niobate single crystals of congruent composition subjected to reducing thermochemical treatment has been investigated by impedance spectroscopy. It has been shown that the subsequent heating of the reduced lithium niobate samples in dry air up to 380 K or higher is accompanied by the progressive increase in their electric resistance, which is due to the oxidization of the crystal surface layers. © 2017, Pleiades Publishing, Ltd.


Novosad S.S.,Ivan Franko National University of Lviv | Kostyk L.V.,Ivan Franko National University of Lviv | Novosad I.S.,Ivan Franko National University of Lviv | Solskii I.M.,CARAT Scientific Research Company
Journal of Applied Spectroscopy | Year: 2010

We have studied thermally and photostimulated recombination processes in PbWO4 crystals in the temperature interval 90-295 K. We have shown that after x-ray excitation of the crystal at 90 K, the thermally stimulated luminescence curve shows a relatively intense peak at 110 K and weak peaks at about 173, 191, and 232 K. Exposure of the PbWO4 crystal to IR radiation after excitation by x-ray photons leads to the appearance of photostimulated flash luminescence, a significant decrease in the intensity of the 110 K peak, and a shift of that peak to the 116 K region. But long-wavelength illumination has less of an effect on the intensity and position of the higher temperature peaks. It is assumed that F- centers are formed in the PbWO4 crystal at 90 K during x-ray exposure. The thermal light sum released by IR illumination in the temperature region 90-150 K has a maximum at ≈108 K. The nature of this maximum is connected with the complex centers [Pb3+ + (WO3-F-)]. Optical and thermal degradation of these centers leads to the appearance of emission in the green region of the localized exciton spectrum. © 2010 Springer Science+Business Media, Inc.

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