Structural, transport and magnetic properties of KxCoO2 center dot yH(2)O(x < 0.2,y <= 0.8)
0
Citation
0
Reference
20
Related Paper
Abstract:
Layered potassium cobaltate K0.36CoO2 has been successfully synthesized from KOH fluxes at 480 degrees C. The K0.36CoO2 sample can be oxidized and intercalated with water by treatment in KMnO4 and K2S2O8 solutions. K0.12CoO2 center dot 0.8H(2)O and K0.16CoO2 center dot 0.6H(2)O have been obtained after the KMnO4 and K2S2O8 treatment, respectively. The diffraction peaks of K0.12CoO2 center dot 0.8H(2)O and K0.16CoO2 center dot 0.6H(2)O can be well indexed by a hexagonal cell similar to the monolayer hydrate NaxCoO2 center dot yH(2)O. Afterdehydration, the major phases have an orthorhombic structure similar to Na0.5CoO2 and show semiconductor behavior. Both K0.12CoO2 center dot 0.8H(2)O and K0.16CoO2 center dot 0.6H(2)O are primarily paramagnetic and show metallic behavior. K0.16CoO2 center dot 0.6H(2)O has a spin-glass-like transition or other magnetic fluctuations around 56 K. The spin-glass-like transition or the regions of magnetic phase separation are reduced in K0.12CoO2 center dot 0.8H(2)O due to the increasing of the intercalated water. We also discussed similarities and differences between the structural and physical properties of KxCoO2 and NaxCoO2.Keywords:
Center (category theory)
Orthorhombic crystal system
Cite
Lattice (music)
Hexagonal Lattice
Cite
Citations (1)
Abstract The crystal structures of the alkali double salts [Mg(H 2 O) 6 ] X Br 3 ( X = Rb + , Cs + ) were analyzed in dependence on temperature from laboratory and synchrotron X‐ray powder diffraction data. At room temperature, both compounds are isostructural to [Mg(H 2 O) 6 ](NH 4 )Br 3 ( C 2/ c ; Z = 4; a = 9.64128(6) Å, b = 9.86531(5) Å, c = 13.78613(9) Å, β = 90.0875(5)° for [Mg(H 2 O) 6 ]RbBr 3 ; a = 9.82304(7) Å, b = 9.98043(6) Å, c = 14.0100(1) Å, β = 90.1430(4)° for [Mg(H 2 O) 6 ]CsBr 3 ). At a temperature of T = 358 K, [Mg(H 2 O) 6 ]RbBr 3 undergoes a reversible phase transition towards a cubic perovskite type of structure with the [Mg(H 2 O) 6 ] 2+ octahedron in the cuboctahedral cavity exhibiting 4‐fold disorder ( $Pm{\bar 3}m$ ; a = 6.94198(1) Å at T = 458 K). In case of [Mg(H 2 O) 6 ]CsBr 3 the lattice parameters in dependence on temperature show a distinct kink at T = 340 K, but no symmetry breaking phase transition occurs before decomposition starts. The dominant role of hydrogen bonding with respect to the stability of the crystal structures is discussed.
Isostructural
Cite
Citations (5)
Three new transition metal oxychlorides MBi(SeO3)2(H2O)Cl (M = Co, Ni, Cu) have been first synthesized. They feature a 3D architecture with 2D [Bi(SeO3)2]∞ layers connected by M2O8Cl2 (M = Co, Ni, Cu) dimer structural knots. They are antiferromagnetic semiconductors.
Characterization
Cite
Citations (5)
Crystal (programming language)
Cite
Citations (24)
This research project involved the synthesis of CaBaCo2Fe2O7 and the attempted synthesis of CaBaCo2V2O7 which are both swedenborgite-like compounds. All compounds were made using solid state synthesis and were characterised using powder and single-crystal x-ray diffraction, energy dispersive X-ray spectroscopy (EDS) and magnetization measurements. The CaBaCo2Fe2O7 was determined to belong to the P63mc space group with hexagonal geometry, and the lattice parameters a = 6.331 A, b = 6.331 A and c = 10.2322 A. The magnetisation was measured at 1T from 300K to 10K and resulted in two ordering peaks at 50K and 140K under zero field. The magnetisation against applied field was measured at 7T at 10K and 100K and showed hysteresis at both temperatures. The magnetization measurements showed ferromagnetic and antiferromagnetic ordering in CaBaFe2Co2O7. The crystal growth of CaBaCo2V2O7 resulted in oxidation of the vanadium, and the formation of barium vanadate (R-3 space group, rhombohedral) single crystals. The crystal growth was carried out again using a 37%:63% mixture of CaCl2 and BaCl2 as flux, which reacted with the compound to make Co3O4 and Ca2(VO4)Cl (orthorhombic) . Using CaCl2 as a flux by itself resulted in the formation of a monoclinic unidentified crystal compound with point group P21c.
Monoclinic crystal system
Orthorhombic crystal system
Vanadate
Barium
Crystal (programming language)
Space group
Cite
Citations (0)
Abstract [Ni(CH 3 PO 3 )(H 2 O)] ( 1 ) and [Ni{CH 3 ‐(CH 2 ) 17 ‐PO 3 }(H 2 O)] ( 2 ) were synthesised by reaction of NiCl 2 ⋅6 H 2 O and the relevant phosphonic acid in water in presence of urea. The compounds were characterised by elemental and thermogravimetric analyses, UV‐visible and IR spectroscopy, and their magnetic properties were studied by using a SQUID magnetometer. The crystal structure of 1 was determined “ab initio” from X‐ray powder diffraction data and refined by the Rietveld method. The crystals of 1 are orthorhombic, space group Pmn 2 1 , with a =5.587(1), b =8.698(1), c =4.731(1) Å. The compound has a hybrid, layered structure made up of alternating inorganic and organic layers along the b direction of the unit‐cell. The inorganic layers consist of Ni II ions octahedrally coordinated by five phosphonate oxygen atoms and one oxygen atom from the water molecule. These layers are separated by bilayers of methyl groups and van der Waals contacts are established between them. A preliminary structure characterisation of compound 2 suggests the crystallisation in the orthorhombic system with the following unit‐cell parameters: a =5.478(7), b =42.31(4), c =4.725(3) Å. The oxidation state of the Ni ion in both compounds is +2, and the electronic configuration is d 8 ( S =1), as determined from static magnetic susceptibility measurements above 50 K. Compound 1 obeys the Curie–Weiss law at temperatures above 50 K; the Curie ( C ) and Weiss ( θ ) constants were found to be 1.15 cm 3 K mol −1 and −32 K, respectively. The negative value of θ indicates an antiferromagnetic exchange coupling between near‐neighbouring Ni II ions. No sign of 3D antiferromagnetic long‐range order is observed down to T =5 K, the lowest measured temperature. Compound 2 is paramagnetic above T =50 K, and the values of C and θ were found to be 1.25 cm 3 K mol −1 and −24 K, respectively. Below 50 K the magnetic behavior of 2 is different from that of 1 . Zero‐field cooled (zfc) and field‐cooled (fc) magnetisation plots do not overlap below T =21 K. The irreversible magnetisation, Δ M fc−zfc , obtained as a difference from fc and zfc plots starts to increase at T =20 K, on lowering the temperature, and it becomes steady at T =5 K. The presence of spontaneous magnetisation below T =20 K indicates a transition to a weak‐ferromagnetic state for compound 2 .
Orthorhombic crystal system
Powder Diffraction
Rietveld Refinement
Cite
Citations (26)
The relationship between the local structure and EPR spectrum is studied by diagonalizing the complete energy matrices for Mn(2+) in a trigonal ligand-field. The results show that the degree of distortion increases with temperature increasing whether it is compressed or elongate distortion, and the distorted tendency of the local structure is different according to the sign of D. Meanwhile, the distortion of Cd(BF(4))(2)center dot 6H(2)O:Mn(2+) system is more sensitive to temperature than that of ZnSnF(6)center dot 6H(2)O:Mn(2+) system. Moreover, the EPR parameter D is closely associated with the local structure parameters R and h while (a - F) is mainly concerned with R. (C) 2010 Elsevier B. V. All rights reserved.
Center (category theory)
Distortion (music)
Cite
Citations (0)
Abstract For Abstract see ChemInform Abstract in Full Text.
Electrosynthesis
Characterization
Cite
Citations (0)
$X$-band EPR measurements on ${\mathrm{Mn}}^{2+}$-doped single crystals of Zn ${({\mathrm{CH}}_{3}\mathrm{C}\mathrm{O}\mathrm{O})}_{2}$ \ifmmode\cdot\else\textperiodcentered\fi{}${2\mathrm{H}}_{2}$O, Mg ${({\mathrm{CH}}_{3}\mathrm{C}\mathrm{O}\mathrm{O})}_{2}$ \ifmmode\cdot\else\textperiodcentered\fi{}${4\mathrm{H}}_{2}$O, and Ni ${({\mathrm{CH}}_{3}\mathrm{C}\mathrm{O}\mathrm{O})}_{2}$ \ifmmode\cdot\else\textperiodcentered\fi{}${4\mathrm{H}}_{2}$O have been performed at room, liquid-nitrogen, and liquid-helium temperatures. The spin-Hamiltonian parameters are estimated by the use of a rigorous least-squares-fitting technique especially adapted to electron-nuclear spin-coupled systems, on a digital computer. The ${\mathrm{Mn}}^{2+}$-${\mathrm{Ni}}^{2+}$ exchange constant, using the shift of $g$ value in the paramagnetic nickel salt from that in the isostructural magnesium salt at liquid-helium temperature, has been determined to be 3.81 GHz.
Isostructural
Cite
Citations (16)