A. E. Voloshin

Cs2Ni(SO4)2 · 6H2O (CNSH) crystal: Growth and some properties

Large single crystals of cesium-nickel sulfate hexahydrate Cs2Ni(SO4)2 · 6H2O of optical quality were grown for the first time. The crystal structure and the optical and thermogravimetric properties of this compound were investigated.

Growth and properties of mixed K2NixCo1−x(SO4)2 · 6H2O crystals

Optically homogeneous mixed K2NixCo(1 − x)(SO4)2 · 6H2O crystals are grown from solutions of different compositions by the temperature-reduction technique in static and dynamic regimes. The optical characteristics of the grown crystals are measured: transmittance reaches 80% in the wavelength range of 240–290 nm and no more than 9% in the visible spectral range. The thermal stability of the crystals is studied. It is established that the thermal stability of mixed K2NixCo1 − x(SO4)2 · 6H2O crystals is higher than that of K2Co(SO4)2 · 6H2O crystal. The defects of the mixed crystals grown in static and dynamic regimes are investigated by X-ray topography.

Growth of KDP crystals from solutions with mechanical impurities

Growth of KDP crystals from aqueous solutions with SiO2 particles whose size ranges from 10–2 to 400 μm in the static and dynamic modes has been studied. The effect of mother-solution supersaturation and particle size and concentration on the process of particle capture by a growing crystal is considered as well as types of inhomogeneities formed in the crystal under the influence of these factors. It is shown that the larger the particle size, the higher the probability of particle capture by a crystal. The influence of supersaturation, growth rate, face morphology, and particle concentration on particle capture and defect formation in crystals is also discussed.

Crystal growth and properties of Rb2Ni(SO4)2 · 6H2O (RNSH)

Large single crystals of rubidium nickel hexahydrate Rb2Ni(SO4)2 · 6H2O (RNSH) of optical quality were grown for the first time. The atomic structure of RNSH crystals was refined. A comparative analysis of the crystal structures of (M1+)2Ni(SO4)2 · 6H2O, where M1+ is K, Rb, or Cs, was performed. The solubility curve of RNSH in water was measured. The optical and thermogravimetric properties of RNSH were investigated. The internal defect structure of RNSH crystals was studied by X-ray topography.

Growth of α-NiSO4 · 6H2O crystals at high rates

The high-rate growth of nickel sulfate hexahydrate NiSO4 · 6H2O (α-NSH) crystals up to 120 × 120 × 65 mm3 in size is described for the first time. The data on the distribution of related impurities in the {011} and {001} growth sectors of α-NSH crystals grown at different rates are reported. The transmission spectra of both growth sectors of these crystals are obtained. The structural quality and the optical properties of rapidly and slowly grown α-NSH crystals are compared. It is established that the {011} growth sector of crystals grown at rates exceeding 5 mm/day shows the best characteristics for application in UV filters.

Study of the K2Ni(SO4)2 ∙ 6H2O–K2Co(SO4)2 ∙ 6H2O–H2O diagram and determination of the conditions for growing K2(Ni,Co)(SO4)2 ∙ 6H2O mixed crystals

The phase diagram of the K2Ni(SO4)2 · 6H2O–K2Co(SO4)2 · 6H2O–H2O ternary system is investigated in the temperature range of 30–70°С, and a relationship between the compositions of the equilibrium phases of the K2CoxNi(1–x)(SO4)2 · 6H2O (KCNSH) solid solution and the growth solution is established. It is shown how the salt compositions of the liquid and solid phases change during crystal growth upon slow cooling of solution. A dependence of the lattice parameters of the KCNSH solid solution on the concentration of isomorphic components is experimentally found.

Crystallization in space: Results and prospects

The results of studying crystallization in space are reviewed with focus on the growth of semiconductor and protein crystals. The history of the problem is considered, the influence of microgravity on the crystal growth is investigated, and the main experimental data on crystal growth in zero gravity are analyzed. The studies performed in this field at the Institute of Crystallography, Russian Academy of Sciences (IC RAS), are reviewed in detail.

Elemental analysis of mixed K2NixCo1–x(SO4)2 ∙ 6H2O crystals

Mixed K2NixCo(1–x)(SO4)2 ∙ 6H2O crystals have been grown by spontaneous crystallization and lowering the solution temperature. The samples have been studied by atomic emission spectroscopy and electron probe X-ray microanalysis. A large difference between the contents of isomorphic components in different crystal growth sectors is revealed. The dependence of the crystal composition on the mother liquor composition is plotted. The component distribution along the crystal growth direction is analyzed.

Effect of growth conditions on the functional properties of K2Co(SO4)2·6H2O crystals

K2Co(SO4)2 · 6H2O single crystals of optical quality have been grown and the effect of solution pH on their solubility and transmission spectra has been investigated. A kinetic growth curve is obtained for the (110) face and the onset temperature of dehydration is established for single-crystal samples. The structural quality of single crystals grown at different supersaturations is analyzed.

Anisotropy of microhardness and fracture of (NH4)2Ni(SO4)2 · 6H2O (ANSH) crystals

The Vickers hardness of the (010) and (001) planes in (NH4)2Ni(SO4)2 · 6H2O (ANSH) crystals has been measured. Anisotropy hardness of the first kind is revealed for the (010) plane in ANSH. The hardness anisotropy coefficient k2 was determined to be 1.5. The temperature dependence of the microhardness of the (001) face of ANSH crystals was investigated in the temperature range from 20 to 80°C. The character of fracture of the (100), (010), and (001) planes during indentation with a spherical indenter has been qualitatively determined.