Synthesis, spectroscopic and luminescence properties of Ga-doped γ-Al2O3.

Gallium-doped aluminum oxide (Al1-xGax)2O3 with γ-Al2O3 (spinel) structure has been synthesized by the precursor method using the formate Al1-xGax(OH)(HCOO)2 as a precursor. The examination of Al1-xGax(OH)(HCOO)2 (x = 0.0, 0.1, 0.2, 0.3, 0.4) was carried out by X-ray powder diffraction, Infrared, Raman spectroscopy and differential-thermal methods. The solid solutions γ-(Al1-xGax)2O3 with х≤0.2 have been synthesized by thermolysis of precursors in helium atmosphere at 700 °C; they exhibit white-blue emission under UV excitation, whose intensity lowers with increasing dopant concentration. As an independent method, the DFT calculations confirmed thermodynamically the stability field of γ-(Al1-xGax)2O3 solid solutions and the NMR data on relative abundance of Al and Ga within the tetrahedral and octahedral sites in the metal sublattice. Furthermore, the structural and thermodynamic properties of carbon-containing impurities within these compounds were suggested theoretically as possible models of luminescence emission centers. The experimentally observed Ga-dependent quenching of luminescence was explained using the competition between C2p and Ga4p states within the band gap of γ-Al2O3.

[Chemical composition of different sorts of soybeans and changes under the influence of weather and soil-climatic conditions]. / Khimicheskii sostav semian nekotorykh sortov soi i ego izmenenie pod vliianiem pogodnykh i pochvenno-klimaticheskikh uslovii

The biochemical composition (the content of protein and lipids, the content of essential amino acids in the protein complex, the fatty acid composition of lipids) of seeds of eighteen soyabean varieties cultivated in different soil-climatic zones under various weather conditions was examined. Changes in the biochemical parameters were primarily associated with the genotype of the variety. The effect of weather, soil and climatic conditions was less marked. With an increase of the protein content the concentration of lysine and methionine in proteins tended to decrease. As long as the oil content in seeds grew, the concentration of oleic acid increased and that of linoleic and linolenic acids decreased.