Synthesis and characterization of hexagonal ferrites BaFe12‐2xZnxTixO19 (0 ≤ x ≤ 2) by thermal decomposition of freeze‐dried precursors

Substituted barium hexaferrites, BaFe_12‐2xZn_xTi_xO₁₉ (0 ≤ x ≤ 2), have been synthesized by thermal decomposition of freeze‐dried acetate precursors. Decomposition and phase formation were investigated by means of thermal analysis, XRD and IR spectroscopy. The initially amorphous decomposed precursor reacts to the substituted hexaferrite via a spinel‐like maghemite (γ‐Fe₂O₃) and Zn/Ti containing spinel ferrites. The synthesis method allows a decrease of the reaction temperature and time, necessary for producing a single phase hexaferrite. At relative low reaction temperatures, the substitution rate x shows remarkable differences at different iron sublattices. For x ≤ 0,8 this selective substitution results in an increase of magnetization as x grows. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Soft‐Mode Spectroscopy in Fe:KTa1‐xNbxO3 Crystals

Fe‐doped potassium tantalite niobate, Fe:KTa_1‐xNb_xO₃ (Fe:KTN), crystallizes with x = 0.48 and a perovskite‐type structure in tetragonal system with point group 4mm, conforming space group P4mm. The paraelectric‐ferroelectric structural transition of the Fe:KTN is studied by Raman scattering investigations. A condensed soft lattice vibrational mode at the phase transition has been analyzed. It originates from the symmetric O2/O3‐Nb/Ta‐O3/O2 in‐plane bending of the Nb/TaO₆ group. The soft optical phonon mode concerns the extraordinary transverse optical phonons propagating along the [110] direction. The Raman spectra measured reflect the crystal disorder. Curie temperature measured by two methods is within 353 and 356.5 K.     

Fluorescence properties of Nd3+ doped stoichiometric LiNbO3 fiber single crystals by micro‐pulling down method

Using the micro‐pulling down (μ‐PD) method, 1 and 3 mol% Nd₂O₃ doped near stoichiometric lithium niobate (LiNbO₃) single crystal fibers were grown in 1 mm diameter and 35∼40 mm length. The grown crystal fibers were free of cracks and the homogeneous distribution of Nd³⁺ ion concentrations were confirmed by the electron probe micro analysis. The changes of fluorescence spectra were measured with respect to the Nd³⁺ ion doping concentration. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determination of the phase diagram for the crystallization of L‐asparaginase II by a turbidity technique ‐ part II. ‐MPD and crystallography studies‐

The phase diagram for the crystallization of L‐asparaginase II including the metastable zone width (MZW), in the presence of PEG₆₀₀₀ and ethanol, respectively, has been studied by an online turbidity technique out of the crystallization in solution (see part I of this work 1 ). Here this paper describes a further investigation on constructing a phase diagram including MZW for the crystallization of L‐asparaginase II with a different precipitant agent of 2‐methyl‐2, 4‐pentandiol (MPD). Along with the phase diagram, the single crystal X‐ray data were successfully collected at 100K from a crystal formed in the presence of 26% (v/v) MPD. The crystals indicate an orthorhombic form and belong to the space group of P2₁2₁2₁ with the unit cell parameters a = 93.9, b = 125.77, c = 151.75Å. The crystal diffracted up to a resolution of 2.88 Å.     

Growth and characterization of ferroelectric‐ferroelastic Tb2(MoO4)3 crystals

Transparent and nearly colorless ferroelectric‐ferroelastic β′‐Tb₂(MoO₄)₃ (TMO) single crystals have been grown by the Czochralski (CZ) method. The single crystal structure was investigated by X‐ray powder diffraction and was shown to be a single phase with the structure similar as the β′‐Gd₂(MoO₄)₃ crystal. The optical transparency of the TMO crystal has been measured and the crystal is almost transparent in the visible and near infrared regions. The defects of TMO crystal were evaluated by etching technique and the ferroelectric domain structures were observed by an optical microscope. A high‐resolution X‐ray diffraction analysis demonstrates that the as‐grown TMO crystal possesses relatively high optical quality. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Flux growth of La‐doped lead zirconate stannate titanate antiferroelectric crystals

Relaxor antiferroelectric single crystals lead lanthanum zirconate stannate titanate (PLZST) with the composition around the morphotropic phase boundary (MPB) have been grown by flux method using 50 wt% PbO‐PbF₂‐B₂O₃ as a flux. The obtained crystals are light yellow in color. The XRD patterns revealed that the habitual faces of the obtained crystal are (001). The crystal morphology was studied and related to a layer growth mechanism controlled by two‐dimensional growth. The chemical composition of as‐grown crystal was analyzed by inductively coupled plasma atomic emission spectrometry (ICP), indicating a slight decrease of the amount of Ti compared to the starting materials. The result was verified by the XRD patterns with the phase transformation from the co‐existence of tetragonal and rhombohedra phases to the single tetragonal phase. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Analysis of the crystal structures of 1,3‐di‐tert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazasilol‐2‐ylidene and 1,3‐di‐tert‐butyl‐2,2‐dichloro‐1,3‐diaza‐2‐sila‐4‐cyclopentene

The crystal structures of the title compounds, 1,3‐di‐tert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazasilol‐2‐ylidene, C₁₀H₂₀N₂Si ( 1 ) and 1,3‐di‐tert‐butyl‐2,2‐dichloro‐1,3‐diaza‐2‐sila‐4‐cyclopentene, C₁₀H₂₀N₂SiCl2 ( 3 ) were solved and are reported. Compound ( 1 ) crystallized in space group P mmn and each molecule has a mirror plane, which bisects the C‐C backbone of the N‐C‐C‐N framework. Compound ( 1 ) was also found to have a 2‐fold twin component. In compound ( 3 ) the space group P 2₁/m results with the mirror plane passing through the N‐C‐C‐N backbone. We compare these structures with the gas phase determination previously reported for ( 1 ) and the incomplete single crystal data for ( 3 ). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Properties of AgGa1‐xInxSe2 single crystals grown by Bridgman method

High‐pure and single‐phase AgGa_1‐xIn_xSe₂ (x=0.2) polycrystalline was synthesized by the mechanical and temperature oscillation method. Adopting the modified Bridgman method an integral AgGa_1‐xIn_xSe₂ single crystal with diameter of 14 mm and length of 35 mm has been obtained at the rate of 6 mm/day. It was found that there is a new cleavage face which was (101), and observed the four order X‐ray spectrum of the {101} faces. By the method of DSC analysis the melting and freezing points of the AgGa_1‐xIn_xSe₂ (x=0.2) single crystal were about 828°C and 790°C. The transmission spectra of the AgGa_1‐xIn_xSe₂ (x=0.2) sample of 5×6×2 mm³ were obtained by means of UV and IR spectrophotometer. The limiting frequency was 774.316nm and the band gap was 1.6eV. It can be found in the infrared spectrum that the infrared transmission was above 60% from 4000cm^‐1 to 600cm^‐1. The value of α in 5.3µm and 10.6µm were 0.022cm^‐1 and 0.1cm^‐1 respectively. All results showed that the crystal was of good quality. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth of zirconium‐doped KTiOPO4 crystals in the K2O‐P2O5‐TiO2‐ZrF4 system

Zirconium‐doped KTiOPO₄ (KTP) crystals were grown using a high temperature flux method in the K₂O‐P₂O₅‐TiO₂‐ZrF₄ system. The dopant content in the single crystals with general composition KTi_1‐xZr_xOPO₄ (where x = 0 – 0.026) strongly depends on zirconium concentration in the homogeneous melts. AES‐ICP method and X‐ray fluorescence analysis were used to determine the composition of the obtained crystals. Phase analyses of the products were performed using the powder XRD. The structures of KTiOPO₄ containing different quantities of Zr were refined on the basis of single crystal XRD data. Applying ZrF₄ precursor for zirconium injection into the flux allowed growing the zirconium‐doped KTP crystals at 930–750°C. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photoacoustic studies on the thermal properties of the NLO compound: L‐alaninium maleate

Studies on thermal and optical properties are very essential for a nonlinear optical material. Photoacoustics (PA) is a recently developed non‐destructive testing (NDT) tool for studying such properties. L‐Alaninium maleate (C₃H₈NO₂⁺·C₄H₃O₄^‐), an organic non‐linear optical (NLO) material was synthesized using submerged seed solution method and was characterized by single crystal X‐ray diffraction (XRD) and density. PA technique was used to determine the thermal parameters of LAM crystals. Moreover, possible phase transition analysis was conducted to ascertain the thermal stability. Scanning electron microscopic (SEM) studies were also carried out and crystal‐packing features discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phase‐manipulable synthesis of Cu‐based nanomaterials using ionic liquid 1‐butyl‐3‐methyl‐imidazole tetrafluoroborate

Using the ionic liquid (IL), 1‐butyl‐3‐methyl‐imidazole tetrafluoroborate, and the precursor Cu₇Cl₄(OH)₁₀·H₂O, series of phase‐manipulable Cu‐based nanomaterials were synthesized by hydrothermal and microwave assisted routes, respectively. The structural characters of the as‐prepared CuO, CuO/Cu₂O composites and pure Cu nanoparticles were investigated by XRD, SEM, TEM and HRTEM, and their surface photovoltaic properties were studied by surface photovoltage spectra. Via hydrothermal route Cu²⁺ ions were found to be reduced gradually into Cu⁺ and subsequently Cu⁰ with increasing the IL, and various phase ratio of CuO, Cu₂O and Cu composite nanosheets and pure Cu nanoparticles were obtained. This implies that the IL could function as both a reductant in the oxygen‐starved condition and a template for the nanosheet products. The ¹H‐NMR result of the IL supports it being a reductant. In microwave assisted route, however, only monoclinic single crystalline CuO nanosheets were obtained, which indicates the IL being a template only in oxygen‐rich condition. Therefore, the crystal phase, composition and morphology of the Cu‐based products could be controlled by simply adjusting the quantity of the IL and oxygen in solution routes. The molecular structure of the IL after oxidation reactions was investigated by ¹H‐NMR and a possible reaction mechanism was proposed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of the atmosphere on the growth of LiYF4 single crystal fibers by the micro‐pulling‐down method

Micro‐pulling‐down growth of LiYF₄ single crystal fibers have been performed under different gas atmospheres using stoichiometric LiYF₄ single crystal pieces from prior Czochralski experiments as starting material. Completely transparent and phase pure LiYF₄ single crystal fibers could be obtained after evacuation of the recipient to 2×10^‐6 mbar and subsequent filling with pure (99.995%) CF₄ gas. Using a gas mixture of 5% CF₄ in Argon or pure 5N Argon leads to the formation of micro crystallites of oxofluorides on the surface. Evacuating only to 3 × 10^‐3 mbar leads, independently of atmosphere, to completely white fibers that are heavily contaminated with oxofluorides. DSC measurements of the completely transparent fiber grown under pure CF₄ atmosphere reveal congruent melting behavior. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

pH‐Controlled topologies of two Co(II) complexes based on 5‐Nitro‐1,2,3‐benzenetricarboxylic acid and 1,6‐Bis(1,2,4‐triazole‐1‐yl)hexane

Two new Co(II) coordination polymers, [Co(Hnbta)(bth)]_n ( 1 ) and {[Co₃(nbta)₂(bth)₃(H₂O)]·H₂O}_n ( 2 ), (H₃nbta = 5‐nitro‐1,2,3‐benzenetricarboxylic acid and bth = 1,6‐bis(1,2,4‐triazole‐1‐yl)hexane), have been synthesized under different pH values through hydrothermal reactions. Both complexes were characterized by elemental analysis, IR spectra, thermogravimetric analysis (TGA), and single‐crystal X‐ray crystallography. Complex 1 exhibits a 3D polythreaded network based on 4‐connected sql 2D layer. Complex 2 has a (4,4,5)‐connected trinodal 3D pillar‐layered network with a (4²·6⁴)₂(4²·6⁷·8)₂(6⁴·8²) topology. Magnetic susceptibility measurements indicate that complexes 1 and 2 show weak antiferromagnetic interactions between the adjacent Co(II) ions.     

Crystal and molecular structure of 1‐allyl‐5‐(4‐methylbenzoyl)‐4‐(4‐methylphenyl)pyrimidine‐2(1H)‐thione

The crystal structure of 1‐allyl‐5‐(4‐methylbenzoyl)‐4‐(4‐methylphenyl)pyrimidine‐2(1H)‐thione (C₂₂H₂₀N₂OS) has been determined from three dimensional single crystal X‐ray diffraction data. The title compound crystallizes in the monoclinic space group P 2₁/c, with a = 10.6674(13), b = 10.1077(7), c = 17.9467(19) Å, β = 98.460(9)°, V = 1914.0(3) ų, D_calc = 1.251 g cm^–3, Z = 4. In the title compound, the allyl group shows positional disorder. Molecules are linked by C‐H···O, C‐H···N and C‐H···S intermolecular interactions forming two‐dimensional network. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of rapid thermal annealing on Zn1‐xCdxO layers grown by radio‐frequency magnetron co‐sputtering

Zn_1‐xCd_xO layers were deposited on the sapphire substrate using the radio‐frequency magnetron co‐sputtering system. The grown Zn_1‐xCd_xO layers were carried out in the post‐annealing treatment for 1 min at the 800 °C oxygen‐ambient by the rapid thermal annealing (RTA) method. X‐ray diffraction (XRD) experiment shows that the Zn_1‐xCd_xO layers are changed from the single phase of the hexagonal structure at 0≤x ≤0.08 to the double phase of hexagonal‐and‐cubic structure at x =0.13. Thus, the maximum Cd‐composition ratio with the hexagonal structure was found out to be x =0.08. Also, the crystallinity of Zn_1‐xCd_xO layers at x =0.13 was remarkably improved by the RTA annealing treatment. This crystal quality improvement was thought to be associated with the relaxation of the compressive strain remaining in the Zn_1‐xCd_xO layers. Therefore, the results of XRD and transmittance lead that the crystal quality of the Zn_1‐xCd_xO layers forming the hexagonal ZnO phase is better than that forming the cubic CdO phase. Consequently, the reliable formation and the crystallinity of the Zn_1‐xCd_xO layers were achieved by using the RTA method of short‐time thermal‐annealing at the high temperature. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure of 3‐(3‐nitrophenylhydrazonocarbonyl)‐(1H)‐1,2,4‐triazole

The title compound, C₁₀H₈N₆O₃, was synthesized by the reaction of 3‐(1H)‐1,2,4‐triazole hydrazine with 3‐nitrobenzaldehyde in ethanol. The single crystal structure has been determined by X‐ray analysis. The crystal belongs to monoclinic system, space group p2₁/c with cell constant, a = 8.0214(17) Å, b = 17.334(4) Å, c = 8.9070(18) Å, V= 1179.4(4) ų. An intramolecular N—H...O and N—H…N hydrogen bond are observed between the ‐NH group with O atom of the carbonyl group and the ‐NH group with N atom. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and crystallographic characterization of a chiral complex of (R)‐2‐(pyridin‐2‐ylmethylene)amino‐2′‐hydroxy‐1,1′‐binaphthyl(L) with hydrated nickel(II) acetate

A chiral complex of (R)‐2‐((pyridin‐2‐ylmethylene)amino)‐2′‐hydroxy‐1,1′‐binaphthyl ( L ) with hydrated nickel (II) acetate has been synthesized and spectroscopically characterized. The crystal structure of [NiL₂(CH₃OH)(CH₃COO)]CH₃COO·CH₃OH has been determined by single‐crystal X‐ray diffraction. The complex crystallizes in the orthorhombic space group P 2(1) 2(1) 2(1) with cell constants a = 15.1035 (19), b = 17.836 (2), c = 18.730 (2)Å, α = β = γ = 90.00°, Z = 4. The structure was solved by direct methods and refined to R = 0.0346 (wR₂ = 0.0863). The analytical result of the crystal structure indicates that a pair of L ligands chelate to a Ni (II) atom in an asymmetric fashion with one Ni‐N bond being longer than the other, the Ni (II) atom is further coordinated by one methanol molecule and one acetate anion to form a distorted octahedral geometry. In the crystal of the complex, the coordination cation [NiL₂(CH₃OH)(CH₃COO)]⁺, the uncoordinated methanol molecule and uncoordinated acetate anion are further assembled into one‐dimensional chain structure via intermolecular hydrogen bonds along the a‐axis. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal Structure of RbD2PO4.D2O: A new Hydrate Phase of KDP‐type Compounds

The mono‐hydrate phase as well as the water‐free RbD₂PO₄ (DRDP) is obtained by crystal growth from fully deuterated aqueous solution. Its crystal structure was determined by combined neutron and X‐ray single crystal diffraction. It consists of double layers of PO₄ tetrahedra with D₂O planes in between. The PO₄ groups are linked by fully ordered deuterium bonds O‐D‐O. RbD₂PO₄.D₂O dehydrates below 329(5)K and undergoes a phase transition to RbD₂PO₄ (DRDP).     

Crystal and Molecular Structure of (9R)‐10,11‐dihydro‐6′‐methoxy‐cinchonan‐9‐ol‐4‐chlorobenzoate hydrochloride

The crystal structure of the title compound has been determined by single crystal X‐ray diffraction methods. C₂₇H₂₉N₂O₃Cl.HCl is one of the cinchona alkaloids. It crystallizes in the space group P2₁2₁2₁ with a = 11.745(3), b = 12.353(6), c = 17.253(6) Å and Z = 4. The structure was refined to a final R value of 0.062 for 2155 observed reflections. The C—N distances are unequal in the quinoline ring system. In quinulidine ring, the bonds around N are more tetrahedral. The spatial arrangement and torsion angles show the open conformation of the molecule. The molecular packing is stabilized by hydrogen bonding.     

Growth,structural, thermal and optical studies on L‐glutamic acid hydrobromide – A new semiorganic NLO material

A new semiorganic crystal, L‐glutamic acid hydrobromide, C₅H₁₀NO₄Br (GHB) has been grown from aqueous solution. The single crystal X‐ray analysis of the crystal showed that it belongs to the non‐centrosymmetric P2₁2₁2₁ space group with protonated glutamic acid as cation and bromine as anion. The back‐bone conformations of the amino acid are in cis and trans form. The side‐chain conformations are observed to be in gauche I / trans / cis / trans forms. The characteristic ‘head‐to‐tail’ hydrogen bonding interaction is observed through a chain C(5) motif. Further, the crystal structure is stabilized by an intricate three‐dimensional hydrogen bonding network. TGA/DTA showed that the grown crystals are thermally stable upto 219 °C without any phase transition. The functional groups responsible for the various modes of vibrations were identified by using FTIR spectroscopy. UV‐Vis‐NIR spectra showed that the crystals have excellent transparency in the visible and infrared regions. The second harmonic generation (SHG) conversion efficiency was investigated to explore the NLO characteristics of the material. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)