E. B. Rudneva

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.

Formation of hair inclusions in rapidly grown potassium dihydrogen phosphate crystals

Abstract A special kind of liquid inclusions named “hairs” are described in the present work. These inclusions were observed in the crystals grown from a point seed at rates of 10–30 mm per day in the [001] direction. It was shown that formation of “hair” inclusions cannot be described by known mechanisms. Their occurrence is not connected with the dislocation structure but probably induced by the morphological conditions on growing surface at high growth velocities.

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.

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.

Anomalies of properties in a series of K 2 Co x Ni 1− x (SO 4 ) 2 · 6H 2 O mixed crystals

The microhardness and thermal stability of K2CoxNi1–x(SO4)2 · 6H2O mixed crystals have been investigated. Microhardness peaks and dehydration onset temperatures are found in the composition range x = 0.05–0.23. The observed anomalies of properties are related to the anomalous changes in the structural parameters of the crystals in this composition range with an increase in the cobalt content. It is shown that structural imperfection of the crystals depends on the sectorial inhomogeneity and reaches a maximum at x = 0.43–0.54.

Structural features of the KH2PO4: Cr single crystal

The precision X-ray structural investigation of KH2PO4 (KDP) crystal samples from different growth sectors of a single crystal containing chromium impurities is performed. It is demonstrated that the structure of the sample from the prismatic growth sector is more perfect than the structure of the sample from the pyramidal growth sector. The impurity trapping can lead to the formation of at least four different types of structural defects on the face of the pyramid, whereas only two of them can be formed on the face of the prism. A comparison with the relevant data for the “pure” KDP crystal shows that the number of defects and their character are approximately identical for all samples. The analysis of the IR spectra indicates that nitrate ions are contained in the samples from both growth sectors. Moreover, structurally bound water molecules and OH groups are revealed in the sample from the prismatic sector.