[en] The effect of redox annealing on resistance of ticor monocrystal (α-Al₂O₃:Ti) to ultraviolet radiation is investigated. An increase in their resistance after high-temperature (1800 deg C) annealing in reducing media is detected, which is quite considerable after annealing in carbon-containing medium, as a result of which in ticor monocrystals with titanium mass part up to 3x10^-3% after UV radiation insignificant number of F⁺ centers is formed. 6 refs.; 2 tabs

[en] Study is made of the UV radiation-induced absorption (IA) and thermostimulated luminescence of (α-Al₂O₃ : Ti) depending on the content and valence state of an activator, as well as on a medium of thermal treatment. Specific features of photophenomena in UV-irradiated (α-Al₂O₃ : Ti) are explained by the proposed model of activator-vacancy optical centers. It is shown that the relation of the content of Ti⁴⁺ ions to the density of cation vacancies determines the extremum dependence of IA under the UV excitation of (α-Al₂O₃ : Ti) monocrystals. A decrease in the density of cation vacancies increases the stability of (α-Al₂O₃ : Ti) to the UV excitation

No abstract available

[en] Luminescence in bands with maxima of 510, 550 and 595 nm is observed for the first time on non-irradiated crystal. Radiation in the band with the maximum of 510 nm by spectroscopic characteristics and temperature dependence of radiation intensity is identical with the observed luminescence of crystals irradiated by high-energy particles. Radiation in the 550-595 nm range is observed on samples in which combination of anion vacancies is possible according to growing conditions, and luminescence with the maximum of 510 nm takes place in case of presence of nonstoichiometric aluminium ions. Transmission of charges from centres irradiating in 435 and 595 nm bands to centres with luminescence of 510 nm takes place under γ-radiation. Radiation in the 510 nm band is shown to be associated with interstitial aluminium ion or (AlO)^3- ion-molecule, while 550, 595 nm is associated with aggregation vacancy centres

[en] Nominally pure crystals MgOxAl₂O₃ and MgOx2Al₂O₃ have been studied. The crystals have been irradiated by an 12 MeV electron beam with the integrated flux of 3x10¹⁵ electron/cm^-2. Measurements have been taken of optical absorption spectra and of curves of thermoluminescence of magnesium-aluminium spinel crystals. A crystallographic analysis has shown that in the spinel structure, oxygen ions form an almost perfect close-packed cubic lattice, with Mg and Al ions are in tetraedric (A) and octaedric (B) vacancies formed. On irradiation, free electrons and holes are formed which transform into optically active centers. Absorption spectra of the irradiated crystals of 2Al₂O₃ are presented. When the samples are annealed, the colour centers are destroyed, with a subsequent thermoluminescence (TL). A conclusion may be drawn that irradiation of Mg-Al spinel crystals by 12 MeV electrons leads to intense formation of colour centers with absorption band maxima at 270, 360, 390, 470 and 580 nm. On the TL curves, maxima were observed at 390, 430, 450, 470 and 500 K. A comparison of the absorption bands and TL maxima with the previously observed absorption and TL spectra allows to identify V and F centers, as well as charge exchange of impurity ions during irradiation

[en] The origin and concentration of defects in MgOxnAl₂O₃ (n=1 and 2.5) crystals were investigated after irradiation with reactor neutrons, electrons, X-rays and UV-light. Low efficiency of defect production in cation sublattice are explained by small coefficient of cation site filling

[en] Spectral characteristics (ESR, absorption, thermostimulated luminescence and conductivity) of sapphire crystals grown by the Verneil method, induced crystallization method and Czochralski and Cyropulos methods have been considered. A number of defects has been identified. The crystals grown by the Cyropulos method are shown to have better parameters

No abstract available

[en] Investigations of the interblock misorientation were carried out on SrTiO₃ single crystals by ESR techniques. A method of small block misalignment angle determination is described avoiding the drawbacks. All samples observed have an axial spectrum of Fe³⁺ that can be interpreted as Fe³⁺ ion associated with a nearest-neighbour O^2- vacancy, e.g. an Fe³⁺-V(O^2-) axial centre. Splitting of the ESR line of the paramagnetic Fe³⁺-V(O^2-) centre can be explained accepting the existence of blocks in single crystals with some misalignment of their crystalline axes

[en] Ceramic specimens of solid solutions of the SrTiO₃-BaTiO₃, SrTiO₃-CaTiO₃ systems are synthesized. X-ray phase analysis and measurements of their dielectric properties in 4.2-200 K range are carried out. Exceptea expressed maximum permittivity wkly expressed anomalies are found at temperature epsilon(T) dependence, their concentra tional dependence is studied. It is established that Curie point of strontium titanate is in the range of 100-112. 5 K and that pure SrTiO₃, besides the high-temperature phase transition, has a series of low-temperature phase transitions, the position of which, probably, obeys the dependence Tsub(ptt)=Tsub(0)N (N-an integer, T₀=12.5 K)