Investigations of LiNb1−xTaxO3 nanopowders obtained with mechanochemical method

Nanocrystalline compounds LiNb1−xTaxO3 of various compositions (x = 0, 0.25, 0.5, 0.75, 1) were synthesized by high-energy ball milling of the initial materials (Li2CO3, Nb2O5, Ta2O5) and subsequent high-temperature annealing of the resulting powders. Data on the phase composition of the nanopowders were obtained by X-ray diffraction methods, and the dependence of the structural parameters of LiNb1−xTaxO3 compounds on the value of x was established. As a result of the experiments, the optimal parameters of the milling and annealing runs were determined, which made it possible to obtain single-phase compounds. The Raman scattering spectra of LiNb1−xTaxO3 compounds (x = 0, 0.25, 0.5, 0.75, 1) have been investigated. Preliminary experiments have been carried out to study the temperature dependences of their electrical conductivit

Growing Large Size Complex Oxide Single Crystals by Czochralski Technique for Electronic Devices

This paper is devoted to the use and further development of the single crystal growing technique invented by Professor Jan Czochralski (1885-1953). The possibilities of the Czochralski technique are demonstrated. Further improvements were introduced at the Scientific Research Company "Carat" (Lviv, Ukraine) to grow large size complex oxide single crystals. The paper presents an overview of some single crystals grown with the use of a modified technology. Growth parameters and properties of resulting crystals are summarized to show a high potential of the Czochralski technique as an industrial technology to grow large-size, high quality, and structurally perfect single crystals of complex oxides

NMR Analysis of Mg Ion Localization in LiNbO3LiNbO_{3} Crystal

The analysis of cation sublattices population in magnesium doped $LiNbO_{3}$ crystals is carried out. It is shown that volume concentration of lithium vacancies $(V_{Li})$ monotonously increases with increasing of MgO content in the crystal up to the threshold value. A series of $LiNbO_{3}$ crystals with various concentration of $Mg^{2+}$ were investigated by $\text{}^{7}Li$ and $\text{}^{93}Nb$ Nuclear Magnetic Resonance (NMR). It is concluded that the peculiarities of NMR spectra in Mg-doped $LiNbO_{3}$ crystals can be explained by the formation of defect complexes including $Mg_{Li}$ ions and $V_{Li}$ on the shortest distances between them

NMR Analysis of Mg Ion Localization in LiNbO 3

The analysis of cation sublattices population in magnesium doped $LiNbO_{3}$ crystals is carried out. It is shown that volume concentration of lithium vacancies $(V_{Li})$ monotonously increases with increasing of MgO content in the crystal up to the threshold value. A series of $LiNbO_{3}$ crystals with various concentration of $Mg^{2+}$ were investigated by $\text{}^{7}Li$ and $\text{}^{93}Nb$ Nuclear Magnetic Resonance (NMR). It is concluded that the peculiarities of NMR spectra in Mg-doped $LiNbO_{3}$ crystals can be explained by the formation of defect complexes including $Mg_{Li}$ ions and $V_{Li}$ on the shortest distances between them

Temperature dependence of CaMoO(4) scintillation properties

The perspective of using CaMoO4 as a scintillation target in cryogenic rare event searches has provided strong motivation for the optimisation of this material. A single crystal of CaMoO4, exhibiting high optical quality, was produced and its scintillation light response to particle excitation and its decay time constant were investigated over the 7-300K temperature range. The scintillation at room temperature is strongly affected by thermal quenching. The main decay time constant is found to be 15.7 +/- 0.4 mu s at T= 300K; cooling to 7K increases the scintillation decay time constant to 380 +/- 20 mu s. The scintillation efficiency of the CaMoO4 crystal was evaluated by comparison with a reference CaWO4 crystal measured under the same conditions; we estimate the light output of CaMoO4 to be 55 +/- 20% that of CaWO4 at 294K and 95 +/- 30% at 7K. The study confirmed that calcium molybdate optimised for high light yield is a very attractive material for use in cryogenic phonon-scintillation detectors in rare event searches. (c) 2007 Elsevier B.V. All rights reserved

In situ Investigation of OH−OH^{-} Absorption in LiNbO3LiNbO_{3} and LiNbO3:MgOLiNbO_{3}:MgO Crystals during Reducing/Oxidizing Annealing

The work presents experimental results of an in situ investigation of the $OH^{-}$ absorption in pure and MgO-doped $LiNbO_{3}$ crystals during reducing (95% Ar + 5% $H_{2}$) and oxidizing $(O_{2})$ high-temperature treatments in the temperature range from room temperature to 820 K. The absorption spectra measured in situ at high temperatures in reducing/oxidizing atmospheres have been analyzed. The origin of the changes in optical absorption caused by heating of the crystal is discussed in terms of the OH-bonds orientation change

In situ Investigation of OH -

The work presents experimental results of an in situ investigation of the $OH^{-}$ absorption in pure and MgO-doped $LiNbO_{3}$ crystals during reducing (95% Ar + 5% $H_{2}$) and oxidizing $(O_{2})$ high-temperature treatments in the temperature range from room temperature to 820 K. The absorption spectra measured in situ at high temperatures in reducing/oxidizing atmospheres have been analyzed. The origin of the changes in optical absorption caused by heating of the crystal is discussed in terms of the OH-bonds orientation change