Anomalous X-ray scattering study of local structures in the superionic conducting class (CuI)(0.3)(Cu2O)(0.35)(MoO3)(0.35)

The anomalous X-ray scattering (AXS) method using Cu and Mo K absorption edges has been employed for obtaining the local structural information of superionic conducting glass having the composition (CuI)(0.3)(Cu2O)(0.35)(MoO3)(0.35). The possible atomic arrangements in near-neighbor region of this glass were estimated by coupling the results with the least-squares analysis so as to reproduce two differential intensity profiles for Cu and Mo as well as the ordinary scattering profile. The coordination number of oxygen around Mo is found to be 6.1 at the distance of 0.187 nm. This implies that the MoO6 octahedral unit is a more probable structural entity in the glass rather than MoO4 tetrahedra which has been proposed based on infrared spectroscopy. The pre-peak shoulder observed at about 10 nm(-1) may be attributed to density fluctuation originating from the MoO6 octahedral units connected with the corner sharing linkage, in which the correlation length is about 0.8 nm. The value of the coordination number of I- around Cu+ is estimated as 4.3 at 0.261 nm, suggesting an arrangement similar to that in molten CuI.

AM(1-x)Al(x)O(3-x) (A=Na or K; M=Nb or Ta): New anion-deficient Perovskite oxides exhibiting oxide ion conduction

Anion-deficient perovskite oxides of the formula AM(1-x)Al(x)O(3-x) (A = Na or K; M = Nb or Ta) have been prepared for 0 < x less than or equal to 0.5. Diffraction experiments reveal that while the potassium compounds adopt orthorhombic/cubic perovskite structures similar to the parent KNbO3/KTaO3, the sodium compound, NaNb0.5Al0.5O2.5, possesses a brownmillerite/LaSr-CuAlO5-like superstructure. Al-27 NMR spectra show an exclusive tetrahedral oxygen coordination for AI(III) in Na-Nb0.5Al0.5O2.5 (I) and both tetrahedral and octahedral coordination for Al(III) in KNb0.5Al0.5O2.5 (II). The results suggest a long-range and short-range ordering of oxide ion vacancies in I and II respectively. Electrical conductivity measurements show a significant oxide ion conduction for KNb1-xAlxO3-x, with the conductivity increasing with x up to x = 0.5. The differences in the Arrhenius plots of the ionic conductivity of I and II have been rationalized in terms of the long-range and short-range ordering of oxide ion vacancies in the anion-deficient perovskite oxides.

Neutron diffraction study of the coupling between spin, lattice, and structural degrees of freedom in 0.8BiFeO(3)-0.2PbTiO(3)

A powder neutron diffraction study was carried out on 0.8BiFeO(3)-0.2PbTiO(3) in the temperature range 27-1000 degrees C. The system exhibits magnetic transition at similar to 300 degrees C and a rhombohedral (R3c)-cubic (Pm3m) ferroelectric phase transition at similar to 650 degrees C. Anomalous variation in the lattice parameters and the octahedral tilt angle is observed across the magnetic transition temperature. In the magnetic phase, the c parameter is contracted and the octahedral tilt angle is slightly increased. The results suggest coupling between the spin, lattice and structural degrees of freedom. (C) 2011 American Institute of Physics. doi:10.1063/1.3555093]

Reactivity Of Pph3 Toward Ru2cl(O2cme)4 - Synthesis And X-Ray Crystal-Structure Of [Ru(O2cme)(Mecn)2(Pph3)2](Clo4)

A new ruthenium(II) complex of the type [Ru(O2CMe)(MeCN)2(PPh3)2](CiO4) (1) has been isolated from a reaction between Ru2Cl(O2CMe), and PPh3 in MeCN followed by the addition of NaClO4. The structure of 1 is determined by single crystal X-ray studies. The crystal belongs to the monoclinic space group C2/m with the following unit cell dimensions for the C42H39N2O6P2ClRu(M = 866.15): a = 23.295(1)angstrom, b = 23.080(1)angstrom, c = 9.159(1)angstrom, beta = 107.32(1)-degrees, V = 4701(1)angstrom3, Z = 4, D(c) = 1.224 gcm-3, lambda(Mo - K-alpha) = 0.7107 angstrom, mu(Mo - K-alpha) = 4.09 cm-1, T = 293K, R = 0.081 (R(w) = 0.094) for 2860 reflections with I greater-than-or-equal-to 3-sigma(I) and g = 0.015853. In the complex cation, the symmetry about the metal centre is essentially octahedral showing the presence of a chelating acetato, two cis-oriented MeCN and two trans-disposed PPh3 ligands. The mechanistic aspects of the core cleavage reaction are discussed.

Facial Coordination in BIS[BIS(Benzimidazol-2-Ylmethyl)Amine]Copper(II) Perchlorate Dihydrate - Synthesis, Structure, Spectra and Redox Behavior

The 1:1 and 1:2 cooper(II) complexes with the tridentate compound bis(benzimidazol-2-ylmethyl)amine (L(1)) and its benzimidazole (L(2)) and amine (L(3)) N-methyl-substituted derivatives have been prepared and their spectroscopic properties studied. While the 1:1 complexes are of the type CuLX(2) nH(2)O (X = C/O-4(-), NO3-, Cl- or Br-), the 1:2 complexes are of the type CuL(2) (ClO4)(2) nH(2)O (L = L(1) or L(3), n = 0-4). In all these complexes L acts as a tridentate ligand with the amine nitrogen and both the benzimidazole nitrogens co-ordinating to Cu-II. The complex [CuL(2)(1)][ClO4](2) 2H(2)O crystallises in the monoclinic space group P2(1)/c with a = 9.828(2), b = 9.546(2) and c = 19.906(2) Angstrom and beta = 95.71(1)degrees, for Z = 2. The R value is 0.0635 for 2180 significant reflections. The copper(II) ion has an elongated octahedral geometry with four equatorial benzimidazole and two long-distance axial amine N donors. The Cu-N-bzim and Cu-N-amine distances are 2.011(4) and 2.597(6) Angstrom respectively. Factors favouring facial co-ordination to tridentate ligands are discussed. The 1:1 complexes involve meridonal co-ordination of the ligands, with square-based geometry as revealed by ligand-field and EPR spectral properties. The NMe substitution as in CuL(3)(ClO4)(2) confers low V ($) over tilde$$(max) and high E(1/2) for the cu(II)-Cu-I couple. Most of the 1:1 complexes are less reversible but exhibit E(1/2) values more positive than those of the corresponding 1:2 complexes.

Synthesis, structure and properties of monomeric complexes obtained from the cleavage of a (?-oxo)bis(?-carboxylato) diruthenium(III) core

Reaction of [Ru2O(O(2)CR)(2)(MeCN)(4)(PPh(3))(2)](ClO4)(2) (1) with 1,2-diaminoethane (en) in MeOH-H2O yielded a mixture of products from which a diamagnetic ruthenium(II) complex [Ru(MeCN)(en)(2)(PPh(3))](ClO4)(2) (2) and a paramagnetic ruthenium(III) species [Ru(O(2)CR)(en)(2)(PPh(3))](BPh(4))(2) (3) (R = Ph, a; C6H4-p-Me, b; C6H4-p-OMe, c) were isolated and characterized. The crystal structure of complex 2, obtained by X-ray diffraction analysis, shows a cis arrangement of the unidentate ligands in this octahedral complex. Complex 3 displays an axial EPR spectrum. Complex 2 undergoes two successive irreversible metal-centred one-electron oxidation processes at 1.13 and 1.33 V vs SCE in MeCN-0.1 M [NBu(4)(n)]ClO4 at 50 mV s(-1). The mechanistic aspects of the core cleavage reactions in 1 are discussed.

Mesoporous aluminoborates

Hexagonal, cubic and lamellar aluminoborate mesophases containing octahedral aluminium and tetrahedral boson are prepared and characterized for the first time.

Synthesis, spectral characterization and in vitro microbiological evaluation of novel glyoxal, biacetyl and benzil bis-hydrazone macrocyclic Schiff bases and their Co(II), Ni(II) and Cu(II) complexes

A series of binuclear Co(II), Ni(II) and Cu(II) complexes were synthesized by the template condensation of glyoxal, biacetyl or benzil bis-hydrazide, 2,6-diformyl-4-methylphenol and Co(11), Ni(II) or Cu(II) chloride in a 2:2:2 M ratio in ethanol. These 22-membered macrocyclic complexes were characterized by elemental analyses, magnetic, molar conductance, spectral, thermal and fluorescence studies. Elemental analyses suggest the complexes have a 2:1 stoichiometry of the type (M2LX2]center dot nH(2)O and Ni(2)LX(2)2H(2)O]center dot nH(2)O (where M = Co(II) and Cu(II); L = H2L1, H2L2 and H2L3; X = Cl; n = 2). From the spectroscopic and magnetic studies, it has been concluded that the Co(11) and Cu(11) complexes display a five coordinated square pyramidal geometry and the Ni(II) complexes have a six coordinated octahedral geometry. The Schiff bases and their metal complexes have also been screened for their antibacterial and antifungal activities by the MIC method. (C) 2011 Elsevier Ltd. All rights reserved.

Infrared spectroscopic study of LiCoO2 thin films

Site disorder of Co3+ ions in sputtered films of lithium cobaltite has been examined using infrared spectroscopy. Both transmission and reflectance modes have been used to characterize the nature of IR absorption. It is found that Co3+ in the sputtered films occupy two types of octahedral sites that differ in the nature of second-neighbor environment. Li+ ions exhibit two bands, which may arise from tetrahedral and octahedral site occupancies or from the presence of disordered regions in the films. (C) 2002 Elsevier Science (USA).

Organically templated linear and layered cadmium sulfates

By reacting cadmium salts with H2SO4 in the presence of organic amines or directly with amine sulfates under hydrothermal conditions, it has been possible to prepare three linear cadmium sulfates of linarite topology, with the compositions [H3N(CH2)(2)NH3](2)[CdCl2(SO4)][SO4].H2O, I, [HN(CH2)(6)NH][CdBr2(SO4)], II, [HN(CH2)(6)NH][CdCl2-(SO4)], III. A layered cadmium sulfate of composition [H3N(CH2)(3)NH3][Cd-2(H2O)(2)(SO4)(3)], IV, has also been obtained. These sulfates are the first examples of a family of organically templated metal sulfates with interesting structural features. In the linarite chains, the CdX4O2 (X = Cl, Br) octahedron shares two trans-edges to form an [Mphi(4)] (phi = anionic ligand) chain decorated by the SO4 tetrahedron that adopts a staggered arrangement on either side of the chain. IV is constructed by the fusion of four-membered ring ladders involving edge sharing between the sulfate tetrahedron and metal octahedron. IV appears to be the first member of a family of organically templated metal sulfates containing an octahedral-tetrahedral 2D net wherein the sulfate tetrahedron is connected at all four corners.

The influence of Fe3+ ions at tetrahedral sites on the magnetic properties of nanocrystalline ZnFe2O4

A systematic study on the variation of Mössbauer hyperfine parameters with grain size in nanocrystalline zinc ferrite is lacking. In the present study, nanocrystalline ZnFe2O4 ferrites with different grain sizes were prepared by ball-milling technique and characterised by X-ray, EDAX, magnetisation and Mössbauer studies. The grain size decreases with increasing milling time and lattice parameter is found to be slightly higher than the bulk value. Magnetisation at room temperature (RT) and at 77 K could not be saturated with a magnetic field of 7 kOe and the observed magnetisation at these temperatures can be explained on the basis of deviation of cation distribution from normal spinel structure. The Mössbauer spectra were recorded at different temperatures between RT and 16 K. The values of quadrupole splitting at RT are higher for the milled samples indicating the disordering of ZnFe2O4 on milling. The strength of the magnetic hyperfine interactions increases with grain size reduction and this can be explained on the basis of the distribution of Fe3+ ions at both tetrahedral and octahedral sites.

Transmission electron microscopy study of domain structures in ferroelectric SrBi2Nb2O9 ceramics

A transmission electron microscopy study has been carried out on the domain structures of SrBi2Nb2O9 (SBN) ferroelectric ceramics which belong to the Aurivillius family of bismuth layered perovskite oxides. SBN is a potential candidate for Ferroelectric Random access memory (FeRAM) applications. The 90° ferroelectric domains and antiphase boundaries (APBs) were identified with dark field imaging techniques using different superlattice reflections which arise as a consequence of octahedral rotations and cationic shifts. The 90° domain walls are irregular in shape without any faceting. The antiphase boundaries are less dense compared to that of SrBi2Ta2O9(SBT). The electron microscopy observations are correlated with the polarization fatigue nature of the ceramic where the domain structures possibly play a key role in the fatigue- free behavior of the Aurivillius family of ferroelectric oxides.

Novel ABO(3) oxides related to perovskite and YAlO3 structure types in the La-B-V-O (B = Ni, Cu) systems

The synthesis, structure and magnetic properties of mixed-metal oxides of ABO(3) composition in the La-B-V-O (B = Ni, Cu) systems are described in the present paper. While the B = Ni oxides adopt GdFeO3-like perovskite structure containing disordered nickel and vanadium at the octahedral B site, La3Cu2VO9 crystallizes in a YAlO3-type structure. A detailed investigation of the superstructure of nominal La3Cu2VO9 by WDS analysis and Rietveld refinement of powder XRD data reveal that the likely composition of the phase is La13Cu9V4O38.5, where the Cu and V atoms are ordered in a root13a(h) (a(h) = hexagonal a parameter of YAlO3-like subcell) superstructure. Magnetic susceptibility data support the proposed superstructure consisting of triangular Cu-3 clusters. At low temperatures, the magnetic moment corresponds to S = 1/2 per Cu-3 cluster, while at high temperatures the behavior is Curie-Weiss like, showing S = 1/2 per copper. The present work reveals the contrasting behavior of La-Cu-V-O and La-Ni-V-O systems: while a unique line-phase related to YAlO3 structure is formed around La3Cu2VO9 Composition in the copper system, a continuous series of perovskite-GdFeO3 solid solutions, LaNi1-xVxO3 for 0 less than or equal to x less than or equal to 1/3 seems to be obtained in the nickel system, where the oxidation state of nickel varies from 3+ to 2+.

Synthesis of new (Bi, La)(3)MSb(2)O(11) phases (M = Cr, Mn, Fe) with KSbO(3)-type structure and their magnetic and photocatalytic properties

Synthesis and structure of new (Bi, La)(3)MSb(2)O(11) phases (M = Cr, Mn, Fe) are reported in conjunction with their magnetic and photocatalytic properties. XRD refinements reflect that Bi(3)CrSb(2)O(11), Bi(2)LaCrSb(2)O(11), Bi(2)LaMnSb(2)O(11) and Bi(2)LaFeSb(2)O(11) adopt KSbO(3)-type structure (space group, Pn (3) over bar). The structure can be described through three interpenetrating networks where the first is the (M/Sb)O(6) octahedral network and other two are the identical networks having Bi(6)O(4) composition. The magnetic measurements on Bi(2)LaCrSb(2)O(11) and Bi(2)LaMnSb(2)O(11) show paramagnetic behaviour with magnetic moments close to the expected spin only magnetic moments of Cr(+3) and Mn(+3). The UV-Visible diffuse reflectance spectra are broad and indicate that these materials possess a bandgap of similar to 2 eV. The photocatalytic activity of these materials has been investigated by degrading Malachite Green (MG) under exposure to UV light.

Effect of strain path change on the evolution of texture and microstructure during rolling of copper and nickel

The effect of strain path change during rolling has been investigated for copper and nickel using X-ray diffraction and electron back scatter diffraction as well as crystal plasticity simulations. Four different strain paths namely: (i) unidirectional rolling; (ii) reverse rolling; (iii) two-step cross rolling and (iv) multi-step cross rolling were employed to decipher the effect of strain path change on the evolution of deformation texture and microstructure. The cross rolled samples showed weaker texture with a prominent Bs {1 1 0}< 1 1 2 > and P(B(ND)) {1 1 0}< 1 1 1 > component in contrast to the unidirectional and reverse rolled samples where strong S {1 2 3}< 6 3 4 > and Cu {1 1 2}< 1 1 1 > components were formed. This was more pronounced for copper samples compared to nickel. The cross rolled samples were characterized by lower anisotropy and Taylor factor as well as less variation in Lankford parameter. Viscoplastic self-consistent simulations indicated that slip activity on higher number of octahedral slip systems can explain the weaker texture as well as reduced anisotropy in the cross rolled samples. (C) 2011 Elsevier B.V. All rights reserved.