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Cation Distribution (cation + distribution)
Selected AbstractsChemInform Abstract: Influence of Nickel Substitution on the Cation Distribution and Magnetic Properties of ZnCr2Se4.CHEMINFORM, Issue 47 2001Izabela Jendrzejewska 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] Cation distribution in spinel (Mn,Co,Cr)3O4 at room temperatureJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2010A. Purwanto As part of a study of the long-term operation of solid-oxide fuel cells, three (Mn,Co,Cr)3O4 samples have been synthesized and characterized. X-ray and neutron diffraction patterns from the powder samples at room temperature were measured and the data were co-refined. The neutron data were indispensible in locating Mn, Co and Cr within the crystallographic unit cell with their respective atomic occupancies. Two of these samples have been identified as cubic Mn0.76Co0.58Cr1.66O4 and Mn1.28Co1.72O4. The third is a two-phase sample containing cubic Mn1.66Co1.34O4 and tetragonal Mn2.05Co0.91O4 in a 59.1,(6):40.9,(6)% mass fraction ratio. Cr, which might be introduced from reaction with chromia during oxidation of interconnect materials, exhibits a preference for the octahedral site rather than the tetrahedral site. Without Cr, Mn dominates the octahedral site. [source] Different models for the polar nanodomain structure of PZN and other relaxor ferroelectricsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2008T. R. Welberry Computer simulations have been carried out to test the recently proposed model for the nanodomain structure of relaxor ferroelectrics such as lead zinc niobate (PZN). In this recent model it was supposed that the polar nanodomains are three-dimensional, that the observed diffuse rods of scattering originate from the boundaries between domains and that the Pb displacements may be directed along , or . This is in marked contrast to a previously published model, which described the polar domains as thin plates with Pb displacements confined to the directions within the essentially two-dimensional domains. The present results confirm that and types of Pb displacement are viable possibilities, but the number of domain boundaries required to produce sufficiently strong diffuse rods of scattering means that individual domains cannot be described as three-dimensional and must still be relatively thin. The current work has been carried out with no direct involvement of the B -site cation ordering, which many workers assume is necessary to understand the formation of the polar nanodomains. While it may be true that the B -site cation distribution could provide an underlying perturbation field that might ultimately limit the extent of any polar domain, it is certainly not necessary to produce the observed scattering effects. [source] Manganoan rockbridgeite Fe4.32Mn0.62Zn0.06(PO4)3(OH)5: structure analysis and 57Fe Mössbauer spectroscopyACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2006Günther J. Redhammer The structure of the basic iron phosphate rockbridgeite [iron manganese zinc tris(phosphate) pentahydroxide] was reinvestigated with special emphasis on the cation distribution deduced from new X-ray and 57Fe Mössbauer data. Rockbridgeite is orthorhombic, space group Cmcm, and shows three different Fe sites, one with symmetry, another with m symmetry and the third in a general position. One phosphate group has the P atom on a site with m symmetry, while the other has the P atom at a site with mm symmetry. Two Fe sites are fully occupied by ferric iron, while Mn3+ and Fe2+ are situated at a third, principally Fe, site. Structural data, bond-valence sums and polyhedral distortion parameters suggest a new interpretation of the rockbridgeite 57Fe Mössbauer spectrum. [source] Quantitative X-Ray Spectrum Imaging of Lead Lanthanum Zirconate Titanate PLZT Thin-FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2008Chad M. Parish The high permittivity of Pb(Zr,Ti)O3 and (Pb,La)(Zr,Ti)O3,PZT and PLZT, respectively,thin films and the flexibility of chemical solution deposition (CSD) make solution-derived P(L)ZT thin films extremely attractive for integrated capacitor applications. However, Pb-loss or cation segregation during processing results in degraded properties of the final film. Here, we have extended the use of multivariate statistical analysis (MSA) of energy-dispersive spectroscopy (EDS) spectrum images (SIs) in scanning transmission electron microscopy (STEM) to allow the two-dimensional (2D) quantitative analysis of cation segregation and depletion in P(L)ZT thin films. Quantified STEM-EDS SIs allow high-resolution (< ,10 nm) quantification of these cation distributions. Surface Pb depletion is found after crystallization and is replenished by a unique post-crystallization PbO overcoat+anneal processes. Zr/Ti and La segregation are found to develop in a decidedly nonplanar fashion during crystallization, especially in PLZT 12/70/30 material, highlighting the need for 2D analysis. Quantitative 2D chemical information is essential for improved processing of homogeneous P(L)ZT films with optimal electrical properties. [source] | ||||||||||