Double Salt Formation in the Cu(HCOO)2–Sr(HCOO)2–H2O System

The solubility in the Cu(HCOO)₂–Sr(HCOO)₂–H₂O system has been studied by the method of physico-chemical analysis at 25 and 50 °C. It has been established that two double salts are formed in the system: CuSr₂(HCOO)₆ · H₂O at 25 °C and CuSr(HCOO)₄ · 4 H₂O at 50 °C. The latter salt has not yet been described in the literature. It has been characterized by X-ray powder diffraction and DT and TG analysis. CuSr(HCOO)₄ · 4 H₂O crystallizes in the triclinic system with lattice parameters a = 12.376(6) Å, b = 13.394(4) Å, c = 11.508(6) Å, α = 93.38(3)°, β = 94.01(3)°, γ = 75.04(3)°. Dehydration proceeds in two stages.     

IR and X-Ray Powder Diffraction Studies on Ba2Me(HCOO)6. 4 H2O (Me = Co,Ni, Zn)

It has been established that the double salts Ba₂Me(HCOO)₆. 4 H₂O (Me = Co, Ni, Zn) are isostructural with Ba₂Cu(HCOO)₆. 4 H₂O (trinclinic space group P1 = C¹_i). The infrared spectra of the double salts and their deuterated analogues have been recorded and the internal modes of the formate groups and the water molecules are reported. The analysis of the infrared spectra indicates that some of the internal formate modes (v₃ and v₄) reflect the existence of three crystallographically independent formate ions. The comparatively large frequency separations between the asymmetric and symmetric C–O stretching modes is a criterion for the different C–O bond lengths within each formate groups. The number and the positions of the bands in the high frequency range (4000–2300 cm⁻¹) are evidence for the existence of two inequivalent water molecules. The apearance of four uncoupled O–D modes in the spectra of the isotopically dilute samples shows that the water molecules are asymmetric. The librational modes of the water molecules are discussed as well.     

On the (MgxNi1–x)SeO4 · 6 H2O and (MgxCu1–x)SeO4 · 5 H2O mixed crystal formation

Mixed crystals (Mg_xNi_1–x)SeO₄ · 6 H₂O and (Mg_xCu_1–x)SeO₄ · 5 H₂O have been prepared studying the solubility in the MgSeO₄–NiSeO₄–H₂O and MgSeO₄–CuSeO₄–H_2O systems at 25 °C. It has been shown that the monoclinic structure of MgSeO₄ · 6 H₂O is unstable and undergoes a change into tetragonal structure due to the included nickel ions (about 4 at %). The lattice parameters of (Mg_{xNi 1–x})SeO₄ 6 H₂O have been calculated. It has been established that the magnesium ions incorporate isodimorphously in the crystal structure of CuSeO₄ · 5 H₂O which could be an indication of the existence of MgSeO₄ · 5 H₂O isostructural with the triclinic CuSeO₄ 5 H₂O. The distribution coefficients of the salt components between the liquid and solid phases have been calculated.     

Optical properties of non‐centrosymmetric mixed crystals K2(La1‐x Cex)(NO3)5 · 2 H2O (x = 0.0 – 1.0)

Large single crystals of optical quality of the non‐centrosymmetric orthorhombic potassium rare earth nitrate mixed crystals K₂(La_1–x Ce_x)(NO₃)₅ · 2 H₂O were grown at 38 °C from diluted HNO₃. For crystals with x = 0.0, 0.19, 0.38 and 0.66 refractive indices and their dispersion were determined with an error less than 1 · 10^–4 in the wavelength range 0.404 – 1.083 μm by the prism method. Phase matching conditions for collinear SHG frequency conversion were analysed in detail, including calculation of the effective nonlinear optical susceptibility. By an appropriate choice of the fraction x of cerium the mixed crystals K₂(La_1–x Ce_x)(NO₃)₅ · 2 H₂O allow an adjustment of non‐critical type I phase matching conditions to a desired wavelength of the fundamental wave within the range 1.055(4) – 1.107(6) μm. Non‐critical type II phase matching can be tuned in the wavelength range 0.949(2) – 0.931(2) μm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Infra-red and Raman Spectra of the Solid Solutions in the KNO3–NH4NO3–H2O System at 298 K

The infra-red and Raman spectra of the solid solutions forming in the KNO₃–NH₄NO₃–H₂O system have been made. The spectra have been in agreement with the structure of mixed crystals settled previously.     

Growth and thermal studies on pure ADP,KDP and mixed K1‐x(NH4)xH2PO4 crystals

The investigations on the formation of mixed crystals of ammonium dihydrogen orthophosphate (ADP) and potassium dihydrogen orthophosphate (KDP) i.e. potassium ammonium dihydrogen phosphate, K_1‐x(NH₄)_xH₂PO₄ have been presented in this paper. Pure and mixed crystals of ADP and KDP have been grown by slow evaporation technique from the supersaturated solution at an ambient temperature 26±1 °C for ammonium concentration x in the range 0.0 ≤ x ≤ 1.0 in the case of mixed crystals. Crystal compositions were determined by flame atomic absorption spectroscopy and chemical analysis. The results of the X‐ray analysis of the grown crystals are also reported. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study the kinetic process of dehydration and the high temperature phase behaviour. DTA showed the distinct thermal events attributed to dehydration of ADP, KDP and K_1‐x(NH₄)_xH₂PO₄. The results of thermal analysis and chemical analysis are consistent with each other. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Homogenitätsuntersuchungen und Bestimmung der molaren Konzentration x an CdxHg1–xTe mit Hilfe der Elektronenstrahlmikrosonde

The semiconductor Cd_xHg_1–xTe serves as a starting material for the production of infrared detectors with a high detectivity and a small time constant. Cd_xHg_1–xTe single crystals are necessary to manufacture detectors efficiently. The single crystals should not contain segregations and have to include a homogeneous molar concentration x. An electron microprobe X-ray analyzer meets all requirements expected from the measuring method for checking the homogeneity of Cd_xHg_1–xTe crystals. — Results of qualitative and quantitative studies in the microscopical and macroscopical range are presented. Typical defects of the crystals were detected by using the qualitative electron microprobe X-ray analysis. The quantitative analysis was carried out with standard samples. The method for determination of the molar concentration x of the standard samples is described.     

Structural and optical properties of Zn(Mg,Cd)O alloy films grown by remote-plasma-enhanced MOCVD

We report the structural and optical properties of wurtzite-structure Zn(Mg,Cd)O ternary alloys. Wurtzite (0 0 0 1) Zn_1−xCd_xO and Mg_yZn_1−yO films were grown on (11–20) sapphire substrates using remote-plasma-enhanced metalorganic chemical vapor deposition. The large bowing parameters of Zn_1−xCd_xO and Mg_yZn_1−yO ternary alloys are 3.0 and 3.5, respectively, which reflects the large difference of each binary’s electronegativity. We have analyzed the broadening of photoluminescence (PL) in Zn(Mg,Cd)O alloys on alloy content by taking into account the statistical alloy fluctuation and the localization of the exciton, and have clarified that the localization of the exciton strongly affects to PL full-width at half-maximum (FWHM) in Zn(Mg,Cd)O alloys. The alloy broadenings in steady-state PL of Zn(Mg,Cd)O alloys are in good agreement with the calculated tendency by the theoretical model based on the statistical alloy fluctuation, while PL FWHM of Zn_1−xCd_xO is three times larger than the calculated results. Moreover, as another way to confirm alloy broadening, we also have done time-resolved PL measurements and derived the localized depth of the exciton in ZnO-based system, indicating a good agreement with the tendency of PL FWHM broadening.     

Effect of temperature and isomorphic atom substitution on optical absorption edge of TlInS2xSe2(1‐x) mixed crystals (0.25 ≤ x ≤ 1)

The optical properties of the TlInS_2xSe_2(1‐x)mixed crystals (0.25 ≤ x ≤ 1) have been investigated through the transmission and reflection measurements in the wavelength range of 400–1100 nm. The optical indirect band gap energies were determined by means of the analysis of the absorption data. It was found that the energy band gaps decrease with the increase of selenium atoms content in the TlInS_2xSe_2(1‐x)mixed crystals. The transmission measurements carried out in the temperature range of 10–300 K revealed that the rates of change of the indirect band gaps with temperature are γ = –9.2×10^–4 eV/K, –6.1×10^–4 eV/K, –4.7×10^–4 eV/K and –5.6×10^–4 eV/K for TlInS₂, TlInS_1.5Se_0.5, TlInSSe and TlInS_0.5Se_1.5 crystals, respectively. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Elastic and elasto‐optical properties of Rb1–x(NH4)xH2AsO4 mixed crystals studied by Brillouin spectroscopy

The elastic and elasto‐optical properties of Rb_1–x (NH₄)_x H₂AsO₄ mixed crystals were studied by Brillouin spectroscopy at room temperature. The measurements were made on single crystals obtained from the aqueous solution by slow evaporation. The behaviour of bulk phonons propagating in investigated crystals was studied for different polarisations of incident and scattered beam. The components of the tensors of elasto‐optical and elastic properties of the crystals studied were determined. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of thiourea mixed cadmium – lead chloride – a nonlinear optical crystal

Nonlinear optical (NLO) crystal of thiourea mixed cadmium–lead chloride dihydrate Cd[(PbCl₃)(NH₂CSNH₂)].2H₂O (TCCPC) have been grown in solution by slow evaporation technique at room temperature. The powder X‐ray diffraction pattern has been recorded and indexed. The UV‐Vis‐NIR transmittance and FT‐IR spectrum have been recorded in the range 200‐1090 nm and 400‐4000 cm^‐1, respectively. The lower cut‐off wavelength is 280 nm in the UV region, which is higher than that of pure Cd(PbCl₃) (CCPC) crystal. The presence of functional groups has been confirmed by FT‐IR analysis. The TCCPC crystal was characterized by SEM and EDX spectrum. The second harmonic generation (SHG) of the thiourea mixed cadmium–lead chloride (TCCPC) crystal is demonstrated by the Kurtz Perry method using Nd:YAG laser and the results confirm that the grown crystal is roughly three times more efficient than ADP. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electron Paramagnetic Resonance of VO2+ in M2Zn(SeO4)2 · 6H2O(M=K,Rb) Single Crystals

The EPR spectrum of VO²⁺ has been studied in single crystals of K₂Zn(SeO₄)₂ · 6H₂O and Rb₂Zn(SeO₄)₂ ∼ 6H₂O at ∼9.45 GHz. VO²⁺ substitutes for Zn²⁺ have preferential orientations in the lattice. The V = O of the intense vanadyl center is nearly along the longest Zn H₂O direction. Spin-Hamiltonian parameters have been evaluated from single crystal as well as from powder spectra.     

Thermoluminescence and optical absorption studies in γ-irradiated KClxBr1–x mixed crystals

Thermoluminescence (TL) and optical absorption measurements have been carried in γ-irradiated KCl, KBr and various compositions of KCl_xBr_1–x mixed crystals as a function of irradiation time and composition. The position of the main glow peak (high temperature peak) and F-band position are found to vary non-linearly with composition, showing a correlation between colour centers and TL. The TL peaks have been analysed by numerical fitting and the trap depths and frequency factors have been calculated for different compositions of the mixed crystals. The thermal ionisation energy of F-centers has been calculated for the mixed crystals and it is found to vary non-linearly with composition. The results obtained in mixed crystals have been discussed in terms of high disorder present in them.     

Crystal structure of Rb<Subscript>2</Subscript>Mn<Subscript>3</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>[P<Subscript>2</Subscript>O<Subscript>7</Subscript>]<Subscript>2</Subscript>, a new representative of the family of hydrated diphosphates

The crystal structure of Rb₂Mn₃(H₂O)₂[P₂O₇]₂, a new phase obtained in the form of single crystals under hydrothermal conditions in the MnCl₂–Rb₃PO₄–H₂O system, is determined by X-ray diffraction (Xcalibur-S-CCD diffractometer, R = 0.0270): a = 9.374(2), b = 8.367(2), c = 9.437(2) Å, ß = 99.12(2)°, space group P2₁/c, Z = 2, D_x = 3.27 g/cm³. A correlation between the unit-cell parameters and the size of cations forming the crystal structures of isostructural A₂M₃(H₂O)₂[P₂O₇]₂ diphosphates (A = K, NH₄, Rb, or Na; _M = Mn, Fe, Co, or Ni) is revealed. It is shown that, due to the topological similarity, the structures of diphosphates and orthophosphates of the farringtonite structural type can undergo mutual transformations.     

Thermoluminescence studies in KBrxI1–x mixed crystals

Thermoluminescence (TL) studies have been carried out in KBr, KI, and in different compositions of KBr_xI_1–x mixed crystals as a function of X-irradiation time. The TL glow peaks have been analysed and the trap depths and frequency factors have been calculated for different compositions. The complex TL peaks observed in these crystals were isolated by using thermal cleaning technique. The various glow peaks observed in these crystals were attributed to native impurities, first stage and second stage colour centers and the results have been discussed.     

Effect of isomorphic atom substitution on the refractive index and oscillator parameters of TlInS2xSe2(1‐x) (0.25 ≤ x ≤ 1) layered mixed crystals

The optical properties of TlInS_2xSe_2(1‐x)mixed crystals (0.25 ≤ x ≤ 1) have been studied at room temperature through the transmittance and reflectivity measurements in the wavelength range of 400–1100 nm. The spectral dependence of the refractive index for all compositions of studied crystals were obtained. The dispersion of the refractive index is discussed in terms of the Wemple–DiDomenico single‐effective‐oscillator model. The compositional dependencies of refractive index dispersion parameters: oscillator energy, dispersion energy and zero‐frequency refractive index were revealed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermoluminescence of Sr1–xEuxF2 + x Solid Electrolytes

Thermoluminescence (TL) studies have been carried out in different compositions of Sr_1–xEuxF_{2 + x} mixed crystals as a function of X-irradiation time. Three groups of TL glow peaks in the temperature ranges (340, 360 ∼ 370 K), (460 ∼ 475, 540 ∼ 575 K) and (615 ∼ 635, 680 ∼ 720 K) are identified. The growth rates of different glow peaks have been compared with each other to estimate the growth kinetics. The three groups of TL glow peaks are attributed to thermal ionization of radiative impurity centers, different stages of F-centers and other kinds of defect centers such as F-interstitials. The shift in the glow peak maxima is perhaps due to unassociated impurities surrounding F-centers causing a change in configuration. The concentration quenching of TL output due to increased europium is pertinent in Sr_1–xEuxF_{2 + x} mixed system.     

Phase Interaction in the Systems Sodium Selenate – Copper Selenate – Water and Sodium Selenate – Zinc Selenate – Water at 25 °C

The phase equilibrium in the systems Na₂SeO₄–CuSeO₄–H₂O and Na₂SeO₄–ZnSeO₄–H₂O were studied and it was established that new phases were obtained – double salts with a composition: Na₂Cu(SeO₄)₂ · 2 H₂O and Na₂Zn(SeO₄)₂ · 2 H₂O. The fields of phase equilibrium of the double salts in the triple systems were determined. The composition of the new phases was investigated by the Schreinemackers' method of physico-chemical analysis, and the number of the water molecules of crystallization – by thermogravimetrical analysis. An X-ray diffraction analysis of the new phases obtained was done.     

Effect of change of state of aggregation of impurity on tl and microhardness of KClxBr1–x mixed crystals doped with Ca2+

Microhardness and Thermoluminescence (TL) measurements have been made in KCl_xBr_1–x mixed crystals doped with Ca²⁺ impurity. The variation of hardness in undoped and Ca²⁺ doped KCl_xBr_1–x crystals with quenching temperature is investigated. TL studied of KCl_xBr_1–x crystals doped with Ca²⁺, both in as-grown state and after quenching them from various elevated temperatures indicate that the positions of the glow peak which has been attributed to F-centers is found to depend upon the state of dispersion of impurity.     

Crystal and molecular structure of the chiral compound 4–(2–methylbutyloxy)phenyl–4–(2-propenyloxy)-benzoate,C21H24O4

The enantiomeric [(S)-(–)-MBP3B] and the racemic form [(±)-MBP3B] of the title compound with the formula C₃H₅O–C₆H₄–CO₂–C₆H₄–OC₅H₁₁ were studied by single crystal analysis at room temperature. (S)-(–)-MBP3B crystallizes in the orthorhombic space group P2₁2₁2₁ with a = 7.835(3) Å, b = 11.093(6) Å, c = 44.820(3) Å and 8 molecules per unit cell. The structure was determined from 966 reflections with intensities > 3σ. The refinement with isotropic temperature factors leads to R = 0.094. The crystals of the racemic form are monoclinic, space group P2₁/a with a = 7.899(5) Å, b = 11.046(6) Å, c = 22.845(12) Å, β = 99.28(3)°, Z = 4.1236 diffractometer data (I > 3σ) were refined by least-squares methods with anisotropic temperature factors for the non-H atoms to R = 0.070. The packing arrangement for both forms shows a layer-like structure with very similar packing coefficients, k = 0.7085 for the pure enantiomer and k = 0.7014 for the racemic form.