Heat capacity of LiInS2, LiInSe2 and LiInTe2 between 200 and 550 K

The molar heat capacity at constant pressure of LiInS₂, LiInSe₂ and LiInTe₂ was measured in the temperature range from about 200 K to 550 K. An analysis of the experimental data showed that the anharmonic contribution to the heat capacity can be described by a polynomial of fourth order in the temperature. A comparison of the results for the LiInC₂^VI compounds with those for the AgB^IIIC₂^VI and A^IIB^IVC₂^V chalcopyrite compounds showed that the lattice anharmonicity effects are essentially influenced by the specific nature of the Li C^VI bond.     

The crystal and molecular structure of 1,12-dibromododecane,C12H24Br2

The α,ω-dihaloalcanes could serve as model compounds for polyethylenes in further studies of infrared and Raman-spectra. The 1,12-dibromododecane, belonging to this class of compounds, has the monoclinic space group P 2₁/a with the cell parameters a = 24.8 Å, b = 5.40 Å, c = 5.50 Å, β = 99°, Z = 2. The preparation of crystals was very difficult. The crystal finally used gives only few and bad X-ray data measured by film method (equiinclination Weissenberg). Therefore the accuracy of the structure determination is not high, but the result is reliable and has model character for related compounds. All molecules are ordered with their long molecular axes parallel to the (401) planes of the unit cell. There are alternating plane layers of bromine atoms on the one hand and aliphatic parts of the molecules on the other hand, both parallel to the (100)-planes. This molecular arrangement explains well the spectroscopic and crystal optical properties of the structure and also of related compounds like 1,10-dibromodecane and 1,18-dibromooctadecane.     

Growth of Yb-doped Y2O3, Sc2O3, and Lu2O3 single crystals by the micro-pulling-down technique and their optical and scintillation characterization

In this report, growth of Yb-doped sesqui-oxide crystals of Y₂O₃, Sc₂O₃, and Lu₂O₃ by the micro-pulling-down technique and their scintillation performance are discussed. Growth of these crystals is difficult mostly as a result of their extremely high melting point of around 2400 °C. Nevertheless, appropriate design of the thermal zone and careful control of the growth parameters allowed fabrication of these crystals of reasonable quality. Based on the results of measurements of emission spectra under α-ray excitation and pulse height spectra under α-ray and γ-ray excitations, scintillation characteristics of above crystals including emission wavelength and light yields under α-ray and γ-ray excitations were examined. Additionally, decay kinetics of these materials under α-ray excitation were evaluated.     

Imidazolium based ionic liquid crystals: structure,photophysical and thermal behaviour of [Cnmim]Br·xH2O (n = 12, 14; x=0, 1)

The long chain imidazolium halides [C_nmim]Br·xH₂O (n = 10, 12; x = 0, 1) have been synthesized and their structural and thermal behaviour together with their photophysical properties characterized. X‐ray structure analyses of the monohydrates ([C₁₂mim]Br·H₂O: triclinic, P1, no. 2, Z = 2, Pearson code aP112, a = 550.0(5) pm, b = 779.4(5) pm, c = 2296.1(5) pm, α = 81.89(5)°, β = 83.76(5)°, γ = 78.102(5)°, 3523 unique reflections with I_o > 2σ(I_o), R₁ = 0.0263, wR₂ = 0.0652, GooF = 1.037, T = 263(2) K; [C₁₄mim]Br•H₂O: triclinic, P1, no. 2, Z = 12, Pearson code aP11, a = 549.86(8) pm, 782.09(13) pm, c = 2511.3(4) pm, α = 94.86(2)°, β = 94.39(2)°, γ = 101.83(2)°, 2063 unique reflections with I_o > 2σ(I_o), R₁ = 0.0429, wR₂ = 0.0690, GooF = 0.770, T = 293(2) K) show for both compounds similar bilayered structures. Sheets composed of hydrophilic structure regions constituted by positively charged imidazolium head groups, bromide anions and hydrogen bonded water alternate with hydrophobic areas formed by interdigitated long alkyl chains belonging to imidazolium cations with different orientation. Combined differential scanning calorimetry and polarizing optical microscopy shows that the monohydrates as well as the anhydrous imidazolium salts are thermotropic liquid crystals which adopt smectic mesophases. The mesophase region is larger in case of the monohydrates when compared to the anhydrous compounds indicating that water obviously stabilizes the mesophase. All compounds show an intense whitish photoluminescence with short lived (¹π←¹π*) and long lived (¹π←³π*) transitions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Transition metal coordination compounds with the dithiooxalate ligand. Synthesis,spectroscopic studies,crystal structure,and bonding of (C5H5NH)2[Ni(S2C2O2)2]

Several new compounds belonging to the family of bis(dithiooxalato)-nickelate(II) complex anion with the general formula (BH)₂[Ni(S₂C₂O₂)₂], where B=pyridine, 3-methylpyridine, 3-ethylpyridine, 4-methylpyridine, and 4-ethylpyridine (hereafter abbreviated as PYNIDT, M3NIDT, E3NIDT, M4NIDT, and E4NIDT, respectively) have been prepared. PYNIDT, M3NIDT, and E3NIDT are isostructural between them and different from the two other compounds, M4NIDT and E4NIDT, which are also isostructural. All of these compounds crystallize in the monoclinic system, space groupP2₁/n withZ=2. Crystal parameters for PYNIDT are:a=5.793(3),b=14.280(5),c=11.222(3) Å,=97.29(4)°,V=920.8(9) ų,F(000)=468,D _x =1.66,D _o=1.65(1) Mg m^–3,R=0.048, andR _w =0.057 for 1236 observed reflections. The IR and UV-V spectra show that the organic bases are protonated and the anion presents the well-known spectrum for the bis(dithiooxalato)-nickelate(II) anions. Thermogravimetric studies indicate that the compounds are anhydrous. The structure solution of PYNIDT confirms that this compound contains discrete quasi-planar complex [Ni(S₂C₂O₂)₂]^2– anions and (C₅H₅NH)⁺ planar cations linked through hydrogen bonds. The structure stacks into layers where the ions are associated into cationanioncation entities through bifurcated hydrogen bonds.     

Cryoscopic Investigation of Lead Oxide Mixtures with Garnet Forming Oxides,Garnets, and Related Oxide Compounds

The freezing point depression of PbO as solvent caused by the trivalent oxides and oxide compounds Fe₂O₃, Ga₂O₃, Al₂O₃, Bi₂O₃, Y₂O₃, Gd₂O₃, La₂O₃, YFeO₃, Fe₃O₄, Y₃Fe₅O₁₂, Gd₃Ga₅O₁₂, and PbFe₁₂O₁₉ allows to determine the number of particles which are formed from these compounds in the diluted solutions. — We have measured the liquidus temperatures of binary mixtures with the help of a DTA-equipment. In this way the cryoscopic constant K̄_c = 121 ± 16 K · kg · mole⁻¹ of PbO was determined by addition of ZnO, Cu₂O, PbSO₄, and PbF₂, respectively. The experimental results show that the oxides and oxide compounds dissociate in particles which contain only one cation of the solved compound.     

Search for compounds of the NaBaR(BO3)2 family (R = La, Nd, Gd, and Yb) and the new NaBaYb(BO3)2 orthoborate

A search for compounds of the NaBaR(BO₃)₂ composition (where R = La³⁺, Nd³⁺, Gd³⁺, or Yb³⁺) is performed by solid state synthesis and spontaneous crystallization. A new compound, NaBaYb(BO₃)₂, is found in this series. It crystallizes in space group $R\bar 3$ and belongs to the family of sublayer complex orthoborates with isolated BO₃ groups NaBaR(BO₃)₂ (R = Y, Sc, and Yb). Theoretical X-ray powder diffraction patterns of NaBaY(BO₃)₂, NaBaSc(BO₃)₂, and NaBaYb(BO₃)₂ are calculated based on single-crystal data.     

The synthesis and X-ray structural studies of 2-cholesteryl-2-thio-1,3,2-oxathiaphospholane and 2-cholesteryl-2-thio-1,3,2-dithiaphospholane

Two thiophospholane derivatives of cholesterol: 2-cholesteryl-2-thio-1,3,2-oxathiaphospholane (1) and 2-cholesteryl-2-thio-1,3,2-dithiaphospholane (2) were synthesized as new reagents for introducing a cholesteryl moiety at the 5-end of oligonucleotidesvia the phosphorothioate or phosphorodithioate bond. Compounds1 and2 were subjected to structural studies by X-ray methods. Both compounds crystallized in the orthorhombic system, space group P2₁2₁2₁,1 witha=6.283(1) Å,b=12.067(1) Å,c=38.983(3) Å,2 witha=6.371(1) Å,b=11.971(1) Å andc=39.502(3) Å. The five-membered heterocyclic rings of both compounds attain a half-chair conformation in the solid state. In structures of1 and2 a disorder of some atoms is observed. The absolute configuration at the phosphorus atom in1 of the components of diastereoisomeric mixture has been established.     

Synthesis and crystal structures of lithium polyphosphates, LiPO3, Li4H(PO3)5, and LiMn(PO3)3

Polyphosphates of the compositions LiPO₃, Li₄H(PO₃)₅, and LiMn(PO₃)₃ were prepared by the reactions of Li₂CO₃ and MnO₂ with melts of polyphosphoric acids at 240–350°C, and their crystal structures were established. The unit-cell parameters are a = 13.074 Å, b = 5.4068 Å, c = 16.452 Å, β = 99.00°, sp. gr. P2/n; a = 6.6434 Å, b = 7.253 Å, c = 11.399 Å, α = 72.60°, β = 83.36°, γ = 85.32°, sp. gr.; $P\bar 1$ ; a = 8.364 Å, b = 8.561 Å, c = 8.6600 Å, sp. gr. P2₁2₁2₁, respectively. The influence of cations on the structures of the compounds is discussed.     

Specific heat and related properties of some AIIBIVC and AIBIIIC semiconducting compounds between 2 and 300 K

From specific heat measurements of the ternary semiconducting compounds ZnSiP₂, ZnSiAs₂, CdGeAs₂, CuGaSe₂, and CuInTe₂ Debye characteristic temperatures and standard entropy values are calculated within the temperature range from 2 to 300 K.     

Study on the possibility of native oxide removal from GaP and GaAs surface by etching,using model experiments

Crystallites of α-Ga₂O₃, β-Ga₂O₃, GaOOH, GaPO₄ and an amorphous phase have been detected previously on chemically etched GaP- and GaAs surfaces. The same compounds were prepared separately and submitted to solubility study, applying several etchants used in etching practice. It could be observed that the solubility of gallium oxides decreases as the chemically bound water is diminished, the anhydrous β-Ga₂O₃ being almost insoluble. As the same poorly soluble oxide forms were found on etched GaP and GaAs surfaces, the difficulties occurring in etching practice can be connected with their presence.     

New zeotype borophosphates with chiral tetrahedral topology: (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II))

Two new isostructural open‐framework zeotype transition metal borophosphate compounds, (H)_0.5M_1.25(H₂O)_1.5[BP₂O₈]·H₂O (M = Co(II) and Mn(II)) were synthesized by mild hydrothermal method. The structure of compounds were characterized by single‐crystal X‐ray diffraction which have ordered, alternating, vertex‐sharing BO₄, PO₄, and (MO₄)OM(H₂O)₂ groups with hexagonal, P 6₁ 2 2 (No 178) space group and unit cell parameters for Co a = 9.4960(6) Å, c = 15.6230(13) Å, for Mn a = 9.6547(12) Å, c = 15.791(3) Å, Z = 1 for both of them. TGA/DTA analysis, IR spectroscopy were used for characterization. Magnetic susceptibility measurements for both of the compound indicate strong antiferromagnetic interaction between metal centers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Single Crystal Growth,Structure and Physical Property of LiCoO2 and LiNiO2

Abstract

Single crystals of LiCoO₂ and LiNiO₂ have been successfully grown for the first time by a flux method. A single-crystal X-ray diffraction study confirmed trigonal symmetry, and their lattice parameters were a = 2.8161(5) Å and c = 14.0536(5) Å for LiCoO₂, and a = 2.8899(13) Å and c = 14.1938(17) Å for LiNiO₂, respectively. The cation distribution in Li_0.92Ni_1.08O₂ was determined to be (Li_0.74Ni_0.26)_3a[Li_0.18Ni_0.82]_3bO₂ with a final R value of 2.7% by a single-crystal X-ray structure analysis. LiCoO₂ proved to show a semiconducting behavior below room temperature by an in-plane electrical resistivity measurement using the single crystal specimen.     

X‐ray diffraction and magnetization studies of BiFeO3 multiferroic compounds substituted by Sm3+, Gd3+, Ca2+

The multiferroic compounds Bi_0.9Sm_0.1FeO₃, Bi_0.9Gd_0.1FeO₃, Bi_0.9Ca_0.1FeO₃, Bi_0.9Sm_0.05Ca_0.05FeO₃, and Bi_0.9Gd_0.05Ca_0.05FeO₃ were prepared by the conventional ceramic method and were characterized by X‐ray diffraction, vibrating sample magnetometry, and differential scanning calorimetry. The compounds were found to have the rhombohedral perovskite‐like structure, accompanied by a small residual Bi₂Fe₄O₉ impurity phase. Magnetic hysteresis loops with enhanced remnant magnetization and coercive field were obtained for the Gd‐containing compounds. The improvement of magnetic behavior of the Gd‐containing compounds is thought to arise mainly from the partial suppression of the spiral spin structure and the stronger interaction between magnetic ions. The magnetic transition temperatures of the compounds were found to be in the range 300‐310 °C. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structures of two azo compounds, 2-methyl-2-(4-bromphenylazo)-1,3-indandione and 2-methyl-2-(4-ethoxyphenylazo)-1,3-indandione

In the two title compounds, the 2-methyl-1,3-dioxoindan-2-yl and 4-(brom; ethoxy) phenyl groups aretrans with respect to one another. The phenyl ring and the azo group are not coplanar in the two molecules. The five-membered rings of the two compounds adopt an envelope conformation. The crystallographic parameters are as follows: 2-Methyl-2-(4-bromphenylazo)-1,3-indandione (I): monoclinic, P2₁/a witha=8.098(2),b=14.442(2),c=12.554(1)Å, =100.55(2)^o, andD _calc=1.58 g cm^–3 forZ=4; 2-methyl-2-(4-ethoxyphenylazo)-1, 3-indandione (II): monoclinic, P2₁/a witha=8.258(2),b=14.449(1),c=13.559(2)Å, =101.19(1)^o, andD _calc=1.29 g cm^–3 forZ=4.     

Ageing effect on dielectric properties of SnO2, Sb2O3, and their mixed thin films

Thin films of various thicknesses in the form of MIM structures have been prepared from the powders of high purity of SnO₂, Sb₂O₃, and their mixed powders separately by the thermal evaporation technique in a vacuum of 10⁻⁵ Torr. The dielectric properties of these oxide thin films have been studied with ageing time and also with frequency at room temperature. The results obtained have shown that the capacitance and loss tangent of the structures initially fall off rapidly and thereafter they attain a constant value even after ageing the capacitors for about 20 days. The rapid fall of capacitance and loss tangent may be due to the rapid decrease in the density of defects due to ageing time. The results thus obtained on SnO₂, Sb₂O₃, and their mixed thin film capacitors are presented and discussed.     

Thermal expansion in CuAlTe2 compound

The lattice parameters a and c as well as the axial thermal expansion coefficients α ⟂ and α ∥ in the CuAlTe₂ chalcopyrite-type compound are determined as a function of temperature in the range from 80 to 650 K by a X-ray diffractometry technique. The data obtained are used to evaluate the axial ratio c/a, the tetragonal distortion δ = 2 — c/a, the interatomic distances for Cu Te and Al Te bonds and their temperature coefficients. It is found that the thermal expansion behaviour of CuAlTe₂ is similar to that of other CuB^IIIC^VI₂ compounds in having a relatively small expansivity along the c-axis and a large one in the perpendicular direction. When comparing the results for a series of the CuB^IIIC^VI₂ compounds (B Al, Ga, In; C S, Se, Te) it is shown that the correlations between the thermal expansion coefficients α ⟂, α ∥, α_m, dδ/dT and the tetragonal distortion δ, as well as the molar mass of the compound take place.     

Growth,structure, and stoichiometry of epitaxial Cu-III-VI2 films on CaF2 substrates

Thin films of CuInTe₂, CuInSe₂, CuInS₂, CuGaSe₂ and CuGaS₂ were deposited onto (111)-and (100)-oriented CaF₂ substrates by flash evaporation technique. Epitaxial growth occurs at substrate temperatures in the range from 750 to 900 K, dependent on the kind of film material. Contrary to the case of GaAs, GaP and Ge substrates there are always polycrystalline parts. The layers were found to be single phase and crystallizing in the chalcopyrite structure only. The composition of the films varied in dependence on the substrate temperature. In the range of about 700 K a nearly stoichiometric composition was found.     

Growth,structure, and superconducting properties of Bi2Sr2Ca2Cu3O10 and (Bi,Pb)2Sr2Ca2Cu3O10‐y crystals

Large and high‐quality single crystals of both Pb‐free and Pb‐doped high temperature superconducting compounds (Bi_1‐xPb_x)₂Sr₂Ca₂Cu₃O_10‐y (x = 0 and 0.3) were grown by means of a newly developed “Vapour‐Assisted Travelling Floating Zone” technique (VA‐TSFZ). This modified zone‐melting technique was realised in an image furnace and allowed for the first time to grow Pb‐doped crystals by compensating for the Pb losses occurring at high temperature. Crystals up to 3×2×0.1 mm³ were successfully grown. Post‐annealing under high pressure of O₂ (up to 10 MPa at T = 500°C) was undertaken to enhance T_c and improve the homogeneity of the crystals. Structural characterisation was performed by single‐crystal X‐ray diffraction (XRD) and the structure of the 3‐layer Bi‐based superconducting compound was refined for the first time. Structure refinement showed an incommensurate superlattice in the Pb‐free crystals. The space group is orthorhombic, A2aa, with cell parameters a = 27.105(4) Å, b = 5.4133(6) Å and c = 37.009(7) Å. Superconducting studies were carried out by A.C. and D.C. magnetic measurements. Very sharp superconducting transitions were obtained in both kinds of crystals (ΔT_c ≤ 1 K). In optimally doped Pb‐free crystals, critical temperatures up to 111 K were measured. Magnetic critical current densities of 2�10⁵ A/cm² were measured at T = 30 K and μ₀H = 0 T. A weak second peak in the magnetisation loops was observed in the temperature range 40‐50 K above which the vortex lattice becomes entangled. We have measured a portion of the irreversibility line (0.1‐5 Tesla) and fitted the expression for the melting of a vortex glass in a 2D fluctuation regime to the experimental data. Measurements of the lower critical field allowed to obtain the dependence of the penetration depth on temperature: the linear dependence of λ(T) for T < 30 K is consistent with d‐wave superconductivity in Bi‐2223. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Elastic properties of the dithionates Na2S2O6 · 2 H2O,K2S2O6, Rb2S2O6, CaS2O6 · 4H2O and SrS2O6 · 4 H2O

Single crystals of the title compounds having optical quality and dimensions of several cm were grown from aqueous solutions. The elastic and thermoelastic constants were determined from ultrasonic resonance frequencies of thick plates. The true point symmetry of K₂S₂O₆ and Rb₂S₂O₆, which is screened by a hexagonal hypermorphy, could be clearly revealed to be trigonal (32) by the existence of the elastic constant c₁₄. In the case of CaS₂O₆ · 4H₂O and SrS₂O₆ · 4H₂O the constant c₁₄ of the specimens appeared too small to confirm the trigonal symmetry group required from electrooptic and non-linear optic effects unambiguously. The isotypy of K₂S₂O₂ and Rb₂S₂O₆ as well as that of CaS₂O₆ · 4H₂O and SrS₂O₆ · 4H₂O is confirmed by their elastic behaviour. The mean elastic stiffness of dithionates is closely related to that of the corresponding sulphates. In the vicinity of the second-order phase transition of K₂S₂O₆ near 235 K weak anomalies of the temperature derivatives of the longitudinal elastic stiffnesses are observed.