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Optical absorption of Bi12SiO20 crystals containing nonstoichiometry defects in the cation sublattices was studied in the temperature range 80 ÷ 600 K. It is shown that, at absorption coefficients the Urbach rule is fulfilled; while at indirect transitions with the participation of optical phonons take place. The value αt depends on temperature. The parameters of the Urbach rule change regularly when the Bi:Si stoichiometry is violated. The features of the isoabsorption dependences and the parameter σ characterizing the temperature change of the edge absorption are revealed. [ABSTRACT FROM AUTHOR]

Optical-temperature investigations of stationary and photo-induced absorption in undoped and Al (or Ga) doped Bi12SiO20 crystals are discussed. In the wave-number range 22000-4000 cm-1 under temperatures from 80 to 650 K, peculiarities of thermochromic effect have been revealed and temperature dependences of intensity of bands forming photo- and thermochromic effects have been found. A correlation between these dependences and spectra of thermostimulated current is explained. [ABSTRACT FROM AUTHOR]

We present the results of experimental investigations of the processes of excitation and erasure of photochromic effect (PCE) in undoped Bi12SiO20 (BSO) crystals and the BSO crystals doped with Al, Ga and Sn ions (BSO:Al, BSO:Ga and BSO:Sn, respectively). The PCE spectra, the spectra of optical erasure of the PCE (OE PCE), as well as the PCE excitation and PCE erasure functions are obtained. It is demonstrated that the sets of individual components of the PCE spectra for the doped crystals are very similar for different impurity ions, though the intensities of those components are different. Doping of BSO manifests itself in weakening PCE in the blue-green region of the spectrum and its strengthening in the spectral region given by hν = 0.5÷2.0 eV. The OE PCE is almost complete and the components that cannot be erased are observed only for the BSO:Sn crystals. We have evidenced that a limiting photon energy (hν* ≈ 2 eV) exists, for which the photoexcitation leads to the PCE for the crystals staying in their initial stationary state, but erases the PCE if the crystals passed into the state with the maximal saturated PCE. [ABSTRACT FROM AUTHOR]

The correlation between photochromic effect and the effect of inducing the photoconductivity in undoped and Al-, Ga-, Sn-, Cr-, Mn-, V-, Fe-, Cu-, Ag-, Mo-doped Bi 12 SiO 20 single crystals have been investigated. It is shown that the photochromic effect is conditioned by the intra-center optical transitions in deep centers, while the effect of inducing the doped photoconductivity is conditioned by filling of the shallow levels in forbidden zone. Characteristic peculiarities of doped ions influence on the photochromic properties of Bi 12 SiO 20 crystals are studied. [ABSTRACT FROM AUTHOR]

Frequency-temperature characteristics of dielectric permittivity and loss factor of Bi 12 SiO 20 crystals doped by Cr and Mn ions have been carried out in audio frequency range in temperature interval 290 to 800 K. Dielectric anomalies of relaxation (Bi 12 SiO 20 :Cr) and resonance (Bi 12 SiO 20 :Mn) types and Cole-Cole dependences close to linear ones have been observed. The results are discussed on the basis of "screened hopping" model. [ABSTRACT FROM AUTHOR]

Dielectric permittivity was studied in ceramics of relaxor ferroelectric bismuth-sodium titanate Na0.5Bi0.5TiO3. The measurements were performed on as sintered and heat treated in vacuum samples. The diffuse dielectric anomalies associated with the structural phase transitions were observed in as sintered samples. The intense peak of permittivity (emax ~ 104) appeared after heat treating in vacuum. The anomaly of e(T) was contributed by slow polarization processes (f < 10 kHz) and was non-stable, vanishing on heating in air up to ~ 800 K. Temperature and frequency dependencies of e were described by using Cole-Cole model with accounting thermally stimulated decay of the non-stable polarization. It is supposed that the dielectric anomaly is determined by space charge polarization mechanism. Oxygen vacancies V••O and electrons localized on titanium ions Ti′ Ti are assumed to be responsible for the phenomenon observed. [ABSTRACT FROM AUTHOR]

Studies to assess the breeding samples of soft winter wheat by weight of grain from the main ear and determine the indicators of adaptability were conducted at the Bila Tserkva Research and Selection Station (BTRSS) in 2011-2013. The study revealed significant differences in breeding lines in the range of variability of grain mass from the main ear and identified small, medium and significant coefficients of variation, which indicates their excellent response to environmental conditions. It was due to genotype, year conditions and their interaction. Line 42 KS had significantly higher than the standard grain weight of the main ear (0.14 g) and the lowest value of the coefficient of variation (8.7%). According to the indicators of adaptability (GAC, σ²(GxE)gi, σ²SACi, σSACi, etc.) the lines 42 KS, 24 KS and 44 KS were distinguished. There was a significant correlation between the weight of grain from the ear and the weight of 1,000 grains (0.603-0.674) and the direct influence of the weight of grain from the main ear on the weight of grain from the plant and grain yield (0.805-0.942). Selected lines as a result of research (2015-2020) from these populations of soft winter wheat are competitively tested in the conditions of Bila Tserkva Research and Selection Station, forming high grain yields (7.39-8.12 t ha-1) and will be transferred to 2021 for the State variety test for inclusion in the Register of plant varieties suitable for distribution in Ukraine. [ABSTRACT FROM AUTHOR]

The research conducted in 2012-2015 in the forest-steppe zone of Ukraine proved the feasibility to increase crop capacity and the efficiency of nutrient uptake from fertilizers by various potato cultivars when grown in short-term crop rotation in comparison with one-crop system. Short-term crop rotation with the following crop alternation was suggested: field 1 - barley; field 2 - potato; field 3 - vegetable crops. The introduction of this crop rotation allows to increase potato crop capacity by 43 cwt/ha or by 17.3%. Green manure proved to be an alternative of manure. The use of siderate intermediary crops (oil-bearing radish, white mustard and also oat seed, spring wheat) makes it possible to get 165-273 cwt/ha of biomass due to plant vegetative organs and root system. When siderate biomass is embedded, 63-102 kg of nitrogen, 15-31 kg of phosphorus, 67-108 kg of potassium enter the soil, which is equivalent to 15-25 t/ha of manure, and additional application of mineral fertilizers N45P45K45 with them is close in its efficiency to 40 t/ha of manure. The yield increase resulted from green manure application was 16-20% on the average, as compared with the unfertilized plots. When siderates with mineral fertilizers are embedded at a mentioned rate the yield capacity increases by 34-42%. Also the nutrition element uptake from the soil and fertilizers increases (manure, siderates, mineral fertilizers) as well as the coefficient of the use of nutrient substances. The response of the cultivars to the application of organic and mineral fertilizers was determined; the advantage of Shchedryk cultivar over Riviera cultivar was identified. [ABSTRACT FROM AUTHOR]