Crystal growth and optical properties of LuYAG:Ce single crystal

Crystals of Ce³⁺-doped (Lu_xY_1?x)₃Al₅O₁₂ (LuYAG) have been grown and studied by X-ray powder diffraction, emission spectroscopy, excitation spectroscopy and X-ray excited fluorescence spectroscopy. The X-ray powder diffraction pattern revealed that the as-grown LuYAG:Ce crystal possessed the garnet structure. Compared with Ce³⁺-doped Y₃Al₅O₁₂ (YAG), the absorption bands associated with the 4f–5d transition shifted to shorter wavelengths, the emission band that originated from a transition from the lowest 5d level to the ²F ground state of the Ce³⁺ ions shifted to the blue, which was probably due to a larger Stokes shift of the emission, and the reduction of relative intensity of antisite defect emission in the X-ray excited fluorescence spectra revealed that introducing Lu ions into YAG could reduce the antisite defect.     

Synthesis and crystal structure of 3-ammonium-4-hydroxyphenyl sulfonate hemihydrate

The crystal structure of 3-ammonium-4-hydroxyphenyl sulfonate hemihydrate C₆H₃(NH₃)(OH)SO₃ · 0.5H₂O is determined by single-crystal X-ray diffraction. The unit cell parameters are as follows: a = 11.2395(3), b = 10.3814(3), c = 13.7509(4) Å, β = 100.326(1)°, V = 1578.49(8) ų, space group P2₁/n, Z = 4. The crystal structure can be described us a succession of infinite corrugated layers parallel to ab plane. These layers consist of rings formed by four sulfonate molecules located around a center of symmetry. The rings are connected to each other and to water molecules via O-H...O hydrogen bonds. The structure is further stabilized by π-π interactions between phenyl rings of organic entities of successive layers.     

A Novel Coordination Polymer Based on Trinuclear Cobalt Building Blocks Cluster: Synthesis,Crystal Structure,and Properties

The title compound {[Co₃(μ₃-OH)(μ₂-H₂O)2(H₂O)₅(BTC)₂] · 6H₂O} _n (H₃BTC is a 1,3,5-benzenetricarboxylic acid) was prepared and characterized by single crystal and powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric and elemental analyses. The single crystal X-ray diffraction reveals that the title compound consists of 1D infinite zigzag chains which were constructed by trinuclear cobalt cluster and BTC^3– ligand. Neighbouring above-mentioned 1D infinite zigzag chains are further linked by intermolecular hydrogen bonding to form a 3D supermolecular structure. In addition, the luminescent properties of the title compound were investigated.     

Growth and spectroscopic characteristics of Er:YbVO4 crystal

A laser crystal Er³⁺:YbVO₄ has been grown by the Czochralski method with excellent quality. The rocking curve from the (0 0 4) diffraction plane of the as-grown Er³⁺:YbVO₄ crystal was measured and the full-width at half-maximum value was found to be 19.80 in. for the (0 0 4) face. The effective segregation coefficient of Er³⁺ was studied by X-ray fluorescence and the crystal structure was determined by means of X-ray diffraction analysis. The polarized absorption spectra and the fluorescence spectra of Er³⁺:YbVO₄ were measured at room temperature. The spectral parameters were calculated based on the Judd–Ofelt theory, and the intensity parameters Ω₂, Ω₄ and Ω₆ are found to be 5.50×10⁻²⁰, 1.96×10⁻²⁰ and 2.34×10⁻²⁰ cm², respectively. The emission cross-section has been calculated by the Fuechtbauer–Ladenbury method. The spectroscopic parameters of Er³⁺:YbVO₄ are compared with other typical laser hosts.     

Nanostructured crystals of fluorite phases Sr1 − x R x F2 + x and their ordering: 9. The defect crystal and real structure of quenched fluorite phases Sr1 − x Ce x F2 + x (x = 0–0.5)

A Sr_0.7Ce_0.3F_2.3 crystal (CaF₂ type, sp. gr. $Fm\bar 3m$ ), obtained by quenching from melt, has been studied for the first time by X-ray diffraction. Fluorine vacancies and interstitial anions are found in the 8c and 32f sites, respectively. The defect ratio in the Sr_0.7Ce_0.3F_2.3 structure corresponds to the tetrahedral cluster configuration of defects {Sr_{4 ? n} Ce _n F₂₆}. The defect structure of quenched (at a rate of ～25 K/min) crystal differs from that of a crystal grown from melt (cooling at a rate of ～3 K/min) by the displacement of some cations (presumably Ce³⁺) along the threefold axis to the 32f site and the anisotropy of thermal vibrations of ions in the cluster core (F _int(32f)3). The concentration dependence of the lattice parameters of quenched Sr_{1 ? x} Ce _x F_{2 + x} phases (x = 0–0.5) is described by a third-order polynomial: a = 5.80009 + 1.166518 × 10^?3 x ? 1.124969 × 10^?5 x ² + 8.258155 × 10^?8 x ³. The compositional dependence of microdistortions is also nonlinear; maximum microdistortions are observed in the SrF₂ crystal. They decrease with an increase in the cerium concentration x to ～ 0.35. The minimum in the range x = 0.30–0.35 correlates with a composition corresponding to the peak (at x ～ 0.29) in the melting curves of the fluorite phase estimated from the phase diagram of the SrF₂-CeF₃ system (the method of thermal analysis).     

Ordering of cations in the voids of the anionic framework of the crystal structure of catapleiite

The pseudohexagonal crystal structure of the mineral catapleiite Na_1.5Ca_0.2[ZrSi₃(O,OH)₉] · 2(H₂O,F) from the Zhil’naya Valley in the central part of the Khibiny alkaline massif (Kola Peninsula, Russia) is studied by X-ray diffraction (XCalibur-S diffractometer, R = 0.0346): a = 20.100(4), b = 25.673(5), and c = 14.822(3) Å; space group Fdd2, Z = 32, and ρ_calcd = 2.76 g/cm³. Fluorine atoms substituting part of H₂O molecules in open channels of the crystal structure have been found for the first time in the catapleiite composition by microprobe analysis. The pattern of distribution of Na and Ca atoms over the voids of the mixed anionic framework consisting of Zr-octahedra and three-membered rings of Si-tetrahedra accounts for the pronounced pseudoperiodicity along the a and c axes of the pseudohexagonal unit cell and for the lowering of crystal symmetry to the orthorhombic one. It is shown that part of the hydrogen atoms of water molecules is statistically disordered; their distribution correlates with the pattern of the population of large eight-vertex polyhedra by Na and Ca atoms.     

X-ray crystal structure of the complex of enniatin B with KNCS

The crystal structure of the complex of enniatin B, cyclo[-(L-MeVal-D-Hyi)₃-](C₃₃H₅₇N₃O₉), with KNCS is determined by X-ray diffraction [CuKαradiation, R = 0.0594 for 7925 reflections with I > 2 σ(I)]. The crystals belong to the space group P3, a = 24.448(5) Å, c = 23.578(5) Å, V = 12277(9) ų, and Z = 6. The unit cell contains 12 symmetrically independent molecules of the antibiotic, which are located on crystallographic threefold axes. The K⁺ ions are located on the threefold axes and are coordinated by the carbonyl oxygen atoms of the hydroxy acid or amino acid residues of the enniatin molecules to form prisms, twisted prisms, and antiprisms. All the independent enniatin molecules retain the principal conformational features revealed earlier in the structures of enniatin B and its complexes.     

Crystal structure and nonlinear optical properties of the K2UO2(SO4)2 · 2H2O compound at 293 K

Single crystals of potassium uranyl sulfate are grown, and their atomic structure is determined using X-ray diffraction analysis. The compound crystallizes in the orthorhombic crystal system with space group Pna2₁ [a = 13.773(4) Å, b = 7.288(2) Å, c = 11.556(4) Å, R ₁ = 0.033, wR ₂ = 0.0892 for 2630 reflections with I > 2σ(I)]. The crystal structure of the K₂UO₂(SO₄)₂ · 2H₂O compound is built up of two-dimensional infinite, negatively charged layers of the composition [UO₂(SO₄)₂·H₂O] _2∞ ^δ? ], which are linked together through the K⁺ ions. The specific features of the atomic arrangement in the structure of this compound are analyzed, and the second harmonic generation of laser radiation is investigated.     

The influence of strontium substitution in fluorapatite glasses and glass-ceramics

Strontium is often substituted for calcium in order to confer radio-opacity in glasses used for dental cements, biocomposites and bioglass-ceramics. The present paper investigates the influence of substituting strontium for calcium in a glass of the following composition: 4.5SiO₂3Al₂O₃1.5P₂O₅3CaO2CaF₂, having a Ca:P ratio of 1.67 corresponding to calcium fluorapatite (Ca₅(PO₄)₃F). The glasses were characterized by magic angle spinning nuclear magnetic resonance (MAS-NMR), by differential scanning calorimetry (DSC) and X-ray powder diffraction (XRD). The ²⁹Si, ²⁷Al and ³¹P NMR spectra for the glasses with different strontium contents were identical. The ¹⁹F spectra indicated the presence of F-Ca(n) and Al-F-Ca(n) species in the calcium glasses and in the strontium glasses F-Sr(n) and Al-F-Sr(n). It can be concluded that strontium substitutes for calcium with little change in the glass structure as a result of their similar charge to size ratio. The low strontium glasses bulk nucleated to a calcium apatite phase. Intermediate strontium content glasses surface nucleated to a mixed calcium-strontium apatite and the fully strontium substituted glass to strontium fluorapatite.     

Crystal structure of 5-(2′-aminophenyl)-2-dimethylamino-1,3,4-thiadiazole

The crystal structure of 5-(2′-Aminophenyl)-2-dimethylamino-1,3,4-thiazole is determined by X-ray diffraction. The compound is prepared by an unusual recyclization of 3-N, N-dimethylthioureidoquinazolin-4(3H)-one. The crystal is monoclinic, space group P2₁/c, a = 7.420(2) Å, b = 10.466(5) Å, c = 14.752(9) Å, β = 109.2(4)°, ρ_calcd = 1.359 g/cm³, and Z = 4 for the C₁₀H₁₂N₄S composition. The molecule consists of the thiadiazole and phenyl rings and the dimethylamine N(CH₃)₂ and amine NH₂ groups attached to the rings. The molecule as a whole is planar. The dihedral angle between the rings is 8.9°. The N(1) and N(4) atoms in the molecule are bound through the intramolecular interaction (2.76 Å). Molecules, which are linked in pairs by antiparallel hydrogen bonds, form a framework structure.     

Crystal structure of Zn4Na(OH)6SO4Cl·6H2O

The structure of Zn₄Na(OH)₆SO₄Cl·6H₂O, a secondary mineral from Hettstedt, Germany, was determined by single-crystal X-ray diffraction. The crystals are hexagonal,a=8.413(8),c=13.095(24) Å, space group $P\bar 3$ , Z=2. The structure was refined to R=0.0554 and R_w=0.0903 for 970 reflections with I≥3σ(I). The structure can be described as zinc hydroxide layers perpendicular toc, from which sulfates and chlorides extend. The layers are held together by a system of hydrogen bonds involving hexaaquo Na⁺ ions which occupy the interlayer space.     

State of Fe3+ ion and Fe3+ −F− interaction in calcium fluorosilicate glasses

The state of Fe³⁺ ions and Fe³⁺ ?F^? interaction in calcium fluorosilicate glasses xCaF₂·(1- x)CaO·SiO₂) (0 ≤ x ≤ 0.3) containing a small amount of iron were investigated by ESR spectroscopy. Two resonances observed near g = 2.0 and g = 4.3 were assigned to dipole-dipole interacted Fe³⁺ ions and Fe³⁺ ions in a rhombic crystal field, respectively. The fraction of Fe³⁺ ions in a rhombic crystal field decreased and that of dipole-dipole interacted Fe³⁺ ions increased with increasing Fe₂O₃ content. It was found that the quantity of dipole-dipole interacted Fe³⁺ ions depends on the negative partial charge of fluorine ions and shows a maximum at 10 mol% CaF₂ (x = 0.2). The maximum is attributed to the largest difference between absolute values of the ionic potentials of ferric and fluorine ions which is caused by the smallest negative partial charge of flourine at 10 mol% CaF₂.     

Photochemical fabrication of molecular devices

We present a novel way to fabricate electronic devices from a molecular charge transfer salt Ag(DM)₂ by simple illumination, which realizes a junction-structure in the single molecular crystal. The electrical conductivity of the selected parts of samples can be controlled by illimination time and power. The electrical behavior gradually turned semiconducting from metallic one by illumination. X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray absorption fine structure indicated that illumination should transfer some electrons from the conducting DM columns to the Ag ions. The X-ray powder diffraction pattern indicated that original crystal lattice was maintained after the illumination. These observations imply that the illumination practically effected doping (or rather dedoping) on the material.     

Crystal structure of a new modification of lithium vanadate Li3(V,P)O4

The crystal structure of a new phase of lithium vanadate, phosphate Li₃(V,P)O₄ obtained by hydrothermal synthesis in the Li₃PO₄-Li₂CO₃-V₂O₅-H₂O system, is studied by X-ray diffraction (R = 0.0298): a = 6.3050(12), b = 10.921(2), and c = 4.9450(10)Å; space group Pbn2₁, Z = 4, and ρ_calc = 2.543 g/cm³. Specific crystal chemical features of the new compound are analyzed in comparison with related structures having three-dimensional tetrahedral frameworks that offer promise as anode materials in lithiumion batteries.     

Crystal and Molecular Structure of Songorine from the Root of Aconitum szechenyianum Gay

Songorine was isolated from the root of Aconitum szechenyianum Gay and its crystal structure was determined by X-ray single crystal diffraction. The compound compactly packs in an orthorhombic unit cell in the P2₁2₁2₁ space group with unit cell dimensions a = 9.7733(7) Å, b = 13.4892(9) Å, c = 14.8097(10) Å, V = 1952.4(2) Å³ and Z = 4. A series of intricate hydrogen bonds assemble the title compound into a three-dimensional networking structure.     

Synthesis,Crystal Structure,and Biological Activity of 1,3,5-Thimethyl-2,4,6-tris(3'-methyl-1'-imidazoliomethylene)Benzene Perchlorate

The title compound, C₂₄H₃₃C_l3N₆O₁₂(ClO₄)₃, was synthesized and structurally characterized by elemental analysis, IR, MS, HMR and single crystal X-ray diffraction. The crystals are triclinic, sp. gr. P1, Z = 2. The crystal structure is stabilized by C–H···O hydrogen-bonds forming a three-dimensional network. The preliminary biological test showed that the title compound had anti-Mycobacterium phlei 1180 activity.     

Crystal and molecular structure of [Cu(pyrimidine)4]2BF4

The crystal structure of [Cu(pyrimidine)₄]2BF₄ was determined using single crystal X-ray diffraction. The compound crystallizes in the monoclinic space groupP2₁/n, with lattice parametersa=9.9736(8),b=13.872(1),c=16.568(1) Å. β=98.002(1), andZ=8, yielding a calculated density of 1.857 g/cm³. The Jahn-Teller distorted copper coordination sphere is composed of the four pyrimidine ligands in the equatorial positions (ave. Cu?N=2.02 Å) and the longer axial bonds from the copper to one fluorine (ave Cu?F=2.39 Å) on each of the BF ₄ ^? anions. The crystal structure features layers of molecules having interleaved pyrimidine rings: the layers are connected through intermolecular H … F hydrogen bonds.     

Refinement of the crystal structure of the high-temperature phase G 0 in (NH4)2WO2F4 (powder, X-ray, and neutron scattering)

The (NH₄)₂WO₂F₄ compound undergoes a series of phase transitions: G ₀ → 201, K → G ₁ → 160, and K → G ₂, with a significant change in entropy (ΔS ₁ ～ Rln10 at the G ₀ → G ₁ transition), which indicates significant orientational disordering in the G ₀ phase and the order-disorder type of the phase transition. X-ray diffraction is used to identify the crystal structure of the G ₀ phase as rhombohedral (sp. gr. Cmcm, Z = 4), determine the lattice parameters and the positions of all atoms (except hydrogen), and show that [WO₂F₄]^2? ions can form a superposition of dynamic and static orientational disorders in the anionic sublattice. A determination of the orientational position of [NH₄]⁺ ions calls for the combined method of elastic and inelastic neutron scattering. Inelastic neutron scattering is used to determine the state of hindered rotation for ammonium ions in the G ₀ phase. Powder neutron diffraction shows that the orientational disorder of NH₄ ions can adequately be described within the free-rotation approximation.     

Raman investigation of ZnO and Zn1−xMnxO nanocrystals synthesized by precipitation method

Zn_1?xMn_xO nanocrystal samples have been successfully synthesized using the chemical precipitation method in aqueous solution. Comparing with pure ZnO NC, the Raman data recorded from the manganese-doped nanocrystals shows an enhancement of the peaks located at 334 and 439 cm^?1. Besides, a new feature at 659 cm^?1 emerges. X-ray diffraction (XRD) of the as-precipitated nanocrystal samples illustrates that Mn-doping only makes the XRD peaks of the as-precipitated Mn-doped nanocrystals shift towards lower angle values, but the crystal structure of bulk ZnO is still preserved in the Mn-doped samples. Hence, the high quality Zn_1?xMn_xO (x ? 0) nanocrystals are formed through the replacement of zinc ions by manganese ions.     

The crystal and molecular structure of SnBr[N(SiMe3)2]3

The crystal structure of SnBr[N(SiMe₃)₂]₃ has been determined from three-dimensional X-ray diffraction data collected by counter methods. This compound crystallizes in the rhombohedral space groupR3c witha=11.970(3) Å, α=99.06(3)°, andZ=2forD _c> =1.37 g cm^?3. The finalR value was 0.027 based on 608 independent observed reflections. The molecule lies on a crystallographic three-fold axis which contains the Sn and Br atoms. The bromine atom is covalently coordinated to the tin atom at a Sn-Br separation of 2.519(2) Å. The three nitrogen atoms complete the bonding to tin with an Sn-N bond length of 2.056(7) Å.