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Powder Diffraction Study (powder + diffraction_study)
Kinds of Powder Diffraction Study Selected AbstractsNeutron Powder Diffraction Study of a Phase Transition in La0.68(Ti0.95Al0.05)O3JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2006Roushown Ali Crystal structures and structural changes of the compound La0.68(Ti0.95Al0.05)O3 have been studied using neutron powder diffraction data and the Rietveld method in the temperature range from 25° to 592°C. The Rietveld profile-fitting analyses of the neutron data and the synchrotron diffraction profile revealed that the crystal symmetry of the low-temperature phase of La0.68(Ti0.95Al0.05)O3 is orthorhombic Cmmm (2ap× 2ap× 2ap; p: pseudo-cubic perovskite). The unit-cell and structural parameters were successfully refined with the orthorhombic Cmmm for the intensity data measured at 25°, 182°, and 286°C, and with the tetragonal P4/mmm (ap×ap× 2ap) for intensity data obtained at 388° and 592°C. The P4/mmm -to- Cmmm phase transition was found to be induced by tilting of the (TiAl)O6 octahedron. The tilt angle decreased with increasing temperature, reaching 0° at the Cmmm,P4/mmm transition temperature. [source] ChemInform Abstract: Neutron Powder Diffraction Study of the Magnetic and Crystal Structures of SrFe2(PO4)2.CHEMINFORM, Issue 52 2008Alexei A. Belik Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Neutron Powder Diffraction Study of the Orthorhombic to Monoclinic Transition in Sc2W3O12 on Compression.CHEMINFORM, Issue 25 2006Tamas Varga Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Phase Transitions in MnO and FeO at Low Temperatures: A Neutron Powder Diffraction Study.CHEMINFORM, Issue 52 2005A. P. Kantor Abstract For Abstract see ChemInform Abstract in Full Text. [source] Neutron Powder Diffraction Study of Mn-Bearing Hematite, ,-Fe2-xMnxO3, in the Range 0 , x , 0.176.CHEMINFORM, Issue 37 2005V. Baron Abstract For Abstract see ChemInform Abstract in Full Text. [source] Temperature Dependent Neutron Powder Diffraction Study of the Laves Phase Compound TbCo2.CHEMINFORM, Issue 22 2005Z. W. Ouyang Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: A Neutron Powder Diffraction Study of Na1-xSrxTaO3 (x = 0.2 and 0.3).CHEMINFORM, Issue 23 2002S. Y. Istomin Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] High-pressure neutron powder diffraction study of the Im phase of ReO3JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2004J.-E. Jørgensen The structure of ReO3 has been studied over the pressure range from 1.27 to 8.01,GPa by neutron powder time-of-flight diffraction as well as by X-ray diffraction up to 41,GPa using Fluorinert as the pressure-transmitting medium. The cubic phase was found to be stable in the pressure range 0.5 to 13.2,GPa and to be highly compressible with a zero-pressure bulk modulus of Bo = 43,(1),GPa. The neutron data were used in least-squares refinements, showing that the ReO6 octahedra remain almost undistorted, while the Re,O,Re bond angle decreases from 166.5,(1) to 146.4,(3)° within the investigated pressure range of 1.27 to 8.01,GPa. The compression mechanism is also described in terms of sphere-packing models of the oxygen anions. [source] In situ high-temperature powder diffraction study of reversible phase transitions in decagonal Al71.2Co12.8Ni16JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2003Christian Soltmann This experimental work is aimed at confirming and broadening findings of former investigations into the type I,S1 phase transition in Al,Co,Ni quasicrystals. In situ high-temperature synchrotron radiation measurements were carried out on Al71.2Co12.8Ni16 powder samples. The cell parameters were precisely determined at various temperatures in the range 290,1110,K. The data provided a new extended insight into the thermal expansion of Al71.2Co12.8Ni16 and into fundamental properties of the phase transition. [source] Neutron powder diffraction study of the anion-deficient La0.70Sr0.30MnO3.00-, manganitesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2009S. V. Trukhanov Abstract Using powder neutron diffraction method the magnetic structure of the anion-deficient La0.70Sr0.30MnO3.00-, (, = 0, 0.15; 0.20) solid solutions at different temperatures has been defined. It is established that the magnetic structure changes with oxygen vacancies concentration. For the investigated samples the structural phase transitions have not been detected. The obtained data confirm the conception of the magnetic phase state forming for the Sr-doped anion-deficient manganites. In according to this conception in case of orbital ordering absence the lowering of the coordination of the magnetic ion results to change of the indirect superexchange interactions Mn3+ -O-Mn3+ sign from positive to negative. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structure and oxygen mobility in mayenite (Ca12Al14O33): a high-temperature neutron powder diffraction studyACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2007H. Boysen The structure of mayenite, Ca12Al14O33, was investigated by neutron powder diffraction up to 1323,K. It has been described previously as a calcium,aluminate framework, in which 32 of the 33 oxygen anions are tightly bound, containing large cages, 1/6 of them being filled randomly by the remaining `free' oxygen. At ambient temperature excess oxygen was found, corresponding to the composition Ca12Al14O33.5 which was attributed to the presence of hydroxide, peroxide and superoxide radicals in the cages. Above 973,K these are lost under vacuum conditions and the composition becomes stoichiometric. From the refined structural parameters it is concluded that the structure is more adequately described as a relatively stable aluminate framework consisting of eightfold rings of AlO4 tetrahedra with disordered Ca and `free' O distributed within. At high temperatures the density of the `free' oxygen is extremely spread out, with the expansion being related to the high ionic conductivity of this material. Since no continuous density distribution between adjacent cages was found and the `free' O forms bonds with part of the Ca, the diffusion proceeds via a jump-like process involving exchange of the `free' oxygen with framework oxygen. The results confirm the recent theoretical predictions of Sushko et al. [(2006), Phys. Rev. B, 73, 014101-1-10]. [source] Neutron powder diffraction study of orthorhombic and monoclinic defective silicaliteACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2000G. Artioli The crystal structure of silicalite (SiO2) with a substantial amount of structural hydroxyl groups [Si(1,x)O(2,4x)(OH)4x, with 0.08 < x < 0.10] has been refined from neutron powder diffraction data measured using the HRPD instrument at the ISIS pulsed neutron source. Powder data were collected on the as-synthesized orthorhombic sample at 298,K, and on the deuterated monoclinic sample at 100,K. Preferential location of Si-atom vacancies was found on four out of 12 independent T sites in the orthorhombic silicalite [Si(6), Si(7), Si(10) and Si(11)], although the H atoms of the substituting hydroxyl groups could not be located because of the low statistical site occupancy on multiple sites. No significant population of D atoms or of Si vacancies was found in the tetrahedral sites of the monoclinic sample. The detected long-range order of adjacent Si atoms in defective orthorhombic [MFI] structures is compatible with a mechanism of Si vacancy clustering and with the model of hydroxyl nests assumed in the literature on the basis of IR spectroscopic evidence. Crystal data: orthorhombic, Pnma, Z = 8, a = 20.0511,(1), b = 19.8757,(1), c = 13.36823,(9),Å, V = 5327.62,(5),Å3, Dx = 1.798,g,cm,3, Mr = 721.01; monoclinic, P21/n, Z = 4, a = 19.8352,(2), b = 20.0903,(2), c = 13.3588,(1),Å, , = 90.892,(1)°, V = 5322.78,(6),Å3, Dx = 1.799,g,cm,3, Mr = 1442.02. [source] Copper(II) chloride and bromide complexes with 2-methyl-2H -tetrazol-5-amine: an X-ray powder diffraction studyACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010Ludmila S. Ivashkevich The complex catena -poly[[dibromidocopper(II)]-bis(,-2-methyl-2H -tetrazol-5-amine)-,2N4:N5;,2N5:N4], [CuBr2(C2H5N5)2]n, (I), and the isotypic chloride complex catena -poly[[dichloridocopper(II)]-bis(,-2-methyl-2H -tetrazol-5-amine)-,2N4:N5;,2N5:N4], [CuCl2(C2H5N5)2]n, (II), were investigated by X-ray powder diffraction at room temperature. The crystal structure of (I) was solved by direct methods, while the Rietveld refinement of (II) started from the atomic coordinates of (I). In both structures, the Cu atoms lie on inversion centres, adopting a distorted octahedral coordination of two halogen atoms, two tetrazole N atoms and two 5-amine group N atoms. Rather long Cu,Namine bonds allow consideration of the amine group as semi-coordinated. The compounds are one-dimensional coordination polymers, formed as a result of 2-methyl-2H -tetrazol-5-amine ligands bridging via a tetrazole N atom and the amine N atom. In the polymeric chains, adjacent Cu atoms are connected by two such bridges. [source] Disordered structure of ZrW1.8V0.2O7.9 from a combined X-ray and neutron powder diffraction study at 530 KACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009Xi Chen A novel compound, vanadium aliovalent substituted zirconium tungstate, ZrW1.8V0.2O7.9, was prepared with vanadium substituting tungsten rather than the common zirconium substitution. The structure of the high-temperature phase was refined from combined neutron and X-ray powder diffraction data gathered at 530,K. This phase is the disordered centric modification (space group Pa) and the average crystal structure is similar to that of ,-ZrW2O8. The V atom occupies only a W2 site and charge compensation is achieved through oxygen vacancy, i.e. the oxygen vacancy occurs at only the O4 site. [Atom names follow the established scheme; Evans et al. (1996). Chem. Mater.8, 2809,2823.] [source] | ||||||||||