In present paper issues of obtaining strontium bismuthate samples, which cation sublattice has more then 50% of strontium atoms, for the research of photocatalytic properties are investigated. Solid phase synthesis method is suggested as a method of obtaining samples. Critical concentration 75% of strontium atoms in cation sublattice is discovered. If concentration exceeds 75%, formation of strontium bismuthate crystalline lattice is not observed. Shown that usage 35- 40% of strontium carbonate as a co-catalyst lets significantly increase photocatalytic activity of strontium bismuthate.
The electro-optic tensor functioning is considered for crystals of 3m type symmetry at various crystallographic orientations. The most effective schemes of electro-optical phase control when light passes through the crystal are brought to light. It is shown that due to electro-optic effect the phase difference between ordinary and extraordinary beams changes when light wave passes through the crystal plate and the polarization of output radiation also changes. It is proved that, using electro-optic effect, it is possible to convert the light wave polarization for a wide range of radiation limited only by the transmission spectrum of the crystal. We take as an example the LiNbO3 crystal and calculate the range of necessary electric fields to provide its functioning in the half and quarter wave plates mode over the wavelength range of 0.4-4.5 μm.
The study describes use of pyrolytic synthesis method for preparation of visible light calcium bismuthate based photocatalyst. The advantage of the proposed method is that it allows obtaining single-phase, homogeneous samples with various types of crystal lattice and controlled defects. It is shown that it is possible to obtain crystalline calcium bismuthate with the same stoichiometry in the entire region of existence of the solid solution. Synthesized samples of calcium bismuthate have been characterized using the scanning electron microscopy and X-ray analysis. It was found that the scope and conditions of synthesis affect the degree of imperfection of both anionic and cationic sublattice of calcium bismuthate.
In this study, a series of calcium bismuthate samples having a different composition and type of crystal lattice was obtained. The diffuse reflectance spectroscopy found that both factors impact the calcium bismuthate ability to absorb the visible light irradiation. It was shown that the bandgap of synthesized photocatalysts depends on the degree of lattice defects. The catalytic activity of photocatalysts was studied in terms of decomposition rate of methylene blue by visible light in the presence of various samples of calcium bismuthate. It was found that the catalytic activity of calcium bismuthates with orthorhombic crystal lattice is lower than that of similar samples of rhombohedral lattice. Thus, samples with the lowest number of cation sublattice defects have the greatest catalytic activity.
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