L. V. Soboleva

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.

Growth of R2Me(SO4)2 · 6H2O single crystals with due regard for solubility diagrams of the R2SO4-MeSO4-H2O systems (R = K, NH4; Me = Ni, Co)

The optimum conditions for growing R2Me(SO4)2 · 6H2O crystals are found from the analysis of the R2+SO4-Me2+SO4-H2O systems (R = K, NH4; Me = Ni, Co) in the temperature range from 55 to 25°C. A new economical technology for growth of single crystals of double sulfate hexahydrates is developed, which allows the use of starting presynthesized solutions of hydrated or anhydrous K, Ni, Co, and (NH4) sulfates. Transparent K2Ni(SO4)2 · 6H2O, K2Co(SO4)2 · 6H2O, and (NH4)2Ni(SO4)2 · 6H2O crystals (35–55) × (25–40) × 10 mm in size are grown on seeds by the method of slow cooling.

Structure and some physical properties of K2Ni(SO4)2 ⋅ 6H2O crystals

The data obtained from the analysis of the solubility phase diagrams have been used in growth of K2Ni(SO4)2 ⋅ 6H2O crystals. The X-ray diffraction studies of the crystals grown showed that, at room temperature, the crystals belong to the diffraction class 2/m. The crystal structure is similar to the structures of the Tutton salts. The study of the absorption spectra and the differential scanning calorimetry (DSC) revealed a pronounced anomaly in the vicinity of 45–46°C, which seems to be associated with the structural changes in the crystal.

Investigation of X-Ray Natural Circular Dichroism in a CsCuCl 3 Single Crystal: Theory and Experiment

X-ray natural circular dichroism in the near-Cu K edge in a CsCuCl3 single crystal, caused by dipole-quadrupole (E1E2) transitions between electronic states of different parity, has been experimentally and theoretically investigated. Numerical simulation of the experimental X-ray absorption spectrum and circular dichroism has been performed. It is established that a circular dichroism signal is observed in the pre-edge spectral region; therefore, it is mainly due to the localized electronic p-d states.

Y2O3-Al2O3-Nd2O3 phase diagram and the growth of (Y,Nd)3 Al5O12 single crystals

The optimum compositions of the melts used for the growth of yttrium-aluminum garnet (YAG) single crystals with different neodymium contents are determined using the phase diagram of the ternary system Y2O3-Al2O3-Nd2O3 with the binary sections Y3Al5O12-Nd2O3 and Y3Al5O12-Nd3Al5O12. A number of melt compositions characterized by one garnet phase, namely, (Y,Nd)3Al5O12, are established. Single crystals of yttrium-aluminum garnets with a high content of the activator (up to 2.6 wt % Nd) are grown by the Czochralski method.

Compositions of melts for growth of functional single crystals of complex oxides and other compounds

The melt compositions (Mc) are calculated for growing crystals with valuable physical properties. The calculation is based on the compositions of the invariant points of the liquidus curves for 33 congruently and 12 incongruently melting solid phases of 42 fusibility diagrams of binary systems. These systems include Na, Ca, Ba, Mg, and Y aluminates; Bi and Pb germanates; Li, K, Ba, and Bi borates; Ba, Fe, Sr, and Bi titanates; Li, K, Cs, Ba, Zn, Ca niobates; Li, Pb, and Gd molibdates; Pb and Nd tungstates; etc. More than 60 studies with data on the experimentally found melt compositions (Me) for growing the noted crystals are analyzed. It is shown that the melt compositions Mc and Me for growth of congruently and incongruently melting crystals are similar. Large-size stoichiometric crystals of high optical quality are grown using these melt compositions. Nonstoichiometric crystals of low structural quality are grown from melt compositions either corresponding to the stoichiometric ratio of the components (Ms) or similar to the compositions at invariant points (Mi). In these cases, a large difference is observed between the melt compositions Mc, Ms, and Me.

Me2O-P2O5-H2O solubility phase diagrams and growth of MeH2PO4 single crystals (Me = Li, Na, K, Rb, Cs, NH4)

The Me2O-P2O5-H2O solubility phase diagrams are used to determine the optimum compositions and the temperatures for growing crystals of MeH2PO4 solid phases (Me = Li, Na, K, Rb, Cs, NH4). The optimum conditions for dynamic growth of dihydrophosphates of the elements of the first group and ammonium are determined. LiH2PO4, NaH2PO4, NaH2PO4 · 2H2O, NaH2PO4 · H2O, KH2PO4, K(H,D)2PO4, RbH2PO4, CsH2PO4, and (NH4)H2PO4 single crystals are grown on seed from aqueous solutions by the methods of temperature lowering and isothermal evaporation.

Growth of single crystals of NaH2PO4 (NaDP), NaH2PO4 · H2O (NaDP · H2O), and NaH2PO4 · 2H2O (NaDP · 2H2O) sodium dihydrogenphosphate based on the analysis of the Na2O-P2O5-H2O phase diagram

The crystallization conditions for the NaH2PO4, NaH2PO4 · H2O, and NaH2PO4 · 2H2O solid phases have been established from the analysis of the phase diagram of solubility of the ternary Na2O-P2O5-H2O system in the temperature range from 0 to 100°C. Based on these data, the methods for growing sodium dihydrogenphosphate single crystals of the above compositions are developed. The initial components for preparing mother solutions were H3PO4 and NaOH solutions taken in certain weight ratios. For the first time, NaDP, NaDP · H2O, and NaDP · 2H2O single crystals were grown on a seed by the method of temperature decrease. The habits of the NaDP and NaDP · H2O single crystals are determined.

Growth of functional single crystals of complex compounds on the basis of the solubility phase diagrams of ternary systems

The validity of solubility phase diagrams of ternary systems for determining the optimal (concentration and temperature) dynamic growth conditions for single crystals of congruently and incongruently dissolving solid phases is shown. It is found that the optimal composition of the mother liquor for growing solid-phase single crystals corresponds to the solution in the solid-phase solubility curve that is located at the maximum distance from the points of invariant equilibria. More than 40 ternary systems have been used and more than 60 new and known large functional single crystals of stoichiometric composition and optical quality that belong to different chemical classes have been grown on their basis under dynamic conditions.

Compositions of supersaturated solutions for enhanced growth of α-NiSO4 · 6H2O, Me2Ni(SO4)2 · 6H2O, MeH2PO4 [Me = Li, Na, K, Rb, Cs, NH4], and K(HxD1−x)2PO4 single crystals

The possibility of determining the optimal compositions and temperatures of supersaturated solutions for enhanced growth of single crystals of congruently and incongruently dissolving solid phases from the solubility diagrams of ternary systems is shown, and this approach is justified. The NiSO4-H2SO4-H2O, Me2SO4-NiSO4-H2O, and Me2O-P2O5-H2O(D2O) systems have been used to determine the optimal compositions and temperatures of supersaturated solutions for growth of α-NiSO4 · 6H2O, Me2Ni(SO4)2 · 6H2O, MeH2PO4 [Me = Li, Na, K, Rb, Cs, NH4], and K (Hx D1−x)2PO4 (D is deuterium) single crystals.