Browsing by Author "Ling, CD"
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- ItemA (3 + 3)-dimensional “hypercubic” oxide-ionic conductor: type ii bi2o3–nb2o5(ACS Publications, 2013-04-09) Ling, CD; Schmid, S; Blanchard, PER; Petříček, V; McIntyre, GJ; Sharma, N; Maljuk, A; Yaremchenko, AA; Kharton, VV; Gutmann, MJ; Withers, RLThe high-temperature cubic form of bismuth oxide, δ-Bi2O3, is the best intermediate-temperature oxide-ionic conductor known. The most elegant way of stabilizing δ-Bi2O3 to room temperature, while preserving a large part of its conductivity, is by doping with higher valent transition metals to create wide solid-solutions fields with exceedingly rare and complex (3 + 3)-dimensional incommensurately modulated ?hypercubic? structures. These materials remain poorly understood because no such structure has ever been quantitatively solved and refined, due to both the complexity of the problem and a lack of adequate experimental data. We have addressed this by growing a large (centimeter scale) crystal using a novel refluxing floating-zone method, collecting high-quality single-crystal neutron diffraction data, and treating its structure together with X-ray diffraction data within the superspace symmetry formalism. The structure can be understood as an ?inflated? pyrochlore, in which corner-connected NbO6 octahedral chains move smoothly apart to accommodate the solid solution. While some oxide vacancies are ordered into these chains, the rest are distributed throughout a continuous three-dimensional network of wide δ-Bi2O3-like channels, explaining the high oxide-ionic conductivity compared to commensurately modulated phases in the same pseudobinary system. © 2013, American Chemical Society.
- ItemAb initio parametrized polarizable force field for rutile-type SnO2(Springer, 2012-05-01) Miiller, W; Kearley, GJ; Ling, CDWe report a new, polarizable classical force field for the rutile-type phase of SnO2, casserite. This force field has been parametrized using results from ab initio (density functional theory) calculations as a basis for fitting. The force field was found to provide structural, dynamical and thermodynamic properties of tin oxide that compare well with both ab initio and experimental results at ambient and high pressures. © 2012, Springer.
- ItemAlkali metal-modified P2 NaxMnO2: crystal structure and application in sodium-ion batteries(American Chemical Society, 2020-08-18) Sehrawat, D; Rawal, A; Cheong, S; Avdeev, M; Ling, CD; Kimpton, JA; Sharma, NSodium-ion batteries (NIBs) are an emerging alternative to lithium-ion batteries because of the abundance of sodium resources and their potentially lower cost. Here we report the Na0.7MnO2 solid state synthesized at 1000 °C that shows two distinct phases; one adopts hexagonal P2-type P63/mmc space group symmetry, and the other adopts orthorhombic Pbma space group symmetry. The phase ratio of P2 to the orthorhombic phase is 55.0(5):45.0(4). A single-phase P2 structure is found to form at 1000 °C after modification with alkali metals Rb and Cs, while the K-modified form produces an additional minor impurity. The modification is the addition of the alkali elements during synthesis that do not appear to be doped into the crystal structure. As a cathode for NIBs, parent Na0.7MnO2 shows a second charge/discharge capacity of 143/134 mAh g–1, K-modified Na0.7MnO2 a capacity of 184/178 mAh g–1, Rb-modified Na0.9MnO2 a capacity of 159/150 mAh g–1, and Cs-modified Na0.7MnO2 a capacity of 171/163 mAh g–1 between 1.5 and 4.2 V at a current density of 15 mA g–1. The parent Na0.7MnO2 is compared with alkali metal (K, Rb, and Cs)-modified NaxMnO2 in terms of surface morphology using scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy, scanning electron microscopy, 23Na solid-state nuclear magnetic resonance, and X-ray photoelectron spectroscopy and in terms of electrochemical performance and structural electrochemical evolution using in situ or operando synchrotron X-ray diffraction. © 2020 American Chemical Society
- ItemAnion Disorder in Lanthanoid Zirconates Gd2-xTbxZr2O7(American Chemical Society., 2013-08-05) Reynolds, EM; Blanchard, PER; Kennedy, BJ; Ling, CD; Liu, S; Avdeev, M; Zhang, Z; Cuello, GJ; Tadich, A; Jang, LYThe pyrochlore?defect fluorite order?disorder transition has been studied for a series of oxides of the type Gd2?xTbxZr2O7 by a combination of diffraction and spectroscopy techniques. Synchrotron X-ray diffraction data suggest an abrupt transition from the coexistence of pyrochlore and defect fluorite phases to a single defect fluorite phase with increasing Tb content. However neutron diffraction data, obtained at ? ≈ 0.497 Å for all Gd-containing samples to minimize absorption, not only provide evidence for independent ordering of the anion and cation sublattices but also suggest that the disorder transition across the pyrochlore?defect fluorite boundary of Ln2Zr2O7 is rather gradual. Such disorder was also evident in X-ray absorption measurements at the Zr L3-edge, which showed a gradual increase in the effective coordination number of the Zr from near 6-coordinate in the pyrochlore rich samples to near 7-coordinate in the Tb rich defect fluorites. These results indicate the presence of ordered domains throughout the defect fluorite region, and demonstrate the gradual nature of the order?disorder transition across the Gd2?xTbxZr2O7 series. © 2013, American Chemical Society.
- ItemCircularly polarized soft x-ray diffraction study of helical magnetism in hexaferrite(American Physical Society, 2010-03-01) Mulders, AM; Lawrence, SM; Princep, AJ; Staub, U; Bodenthin, Y; García-Fernández, M; Garganourakis, M; Hester, JR; Macquart, RB; Ling, CDMagnetic spiral structures can exhibit ferroelectric moments as recently demonstrated in various multiferroic materials. In such cases the helicity of the magnetic spiral is directly correlated with the direction of the ferroelectric moment and measurement of the helicity of magnetic structures is of current interest. Soft x-ray resonant diffraction is particularly advantageous because it combines element selectivity with a large magnetic cross-section. We calculate the polarization dependence of the resonant magnetic x-ray cross-section (electric dipole transition) for the basal plane magnetic spiral in hexaferrite Ba0.8Sr1.2Zn2Fe12O22 and deduce its domain population using circular polarized incident radiation. We demonstrate there is a direct correlation between the diffracted radiation and the helicity of the magnetic spiral. © 2010, American Physical Society
- ItemCoexistence of ferroelectricity and magnetism in transition-metal-doped n = 3 aurivillius phases(Institute of Physics, 2008-01-16) Sharma, N; Kennedy, BJ; Elcombe, MM; Liu, Y; Ling, CDMagnetic-cation-doped three-layer Aurivillius phases Bi2-xSr2+x(Nb/Ta)(2+x)M1-xO12, x approximate to 0.5 and M = Ru4+, Ir4+ or Mn4+, are shown to have the same orthorhombic space group symmetry and similar dielectric and ferroelectric properties as their (non-magnetic) ferroelectric parent compounds Bi2-xSr2+xNb2+xTi1-xO12, x = 0, 0.5. The magnetic-cation-doped phases also show evidence for short-range ferromagnetic (M = Mn) and antiferromagnetic (M = Ru and Ir) exchange, demonstrating the potential of these naturally layered phases as templates for multiferroic (magnetoelectric) materials. © 2008, Institute of Physics
- ItemCoexistence of spin glass and antiferromagnetic orders in Ba3Fe2.15W0.85O8.72(IOP Publishing, 2012-03-23) Miiller, W; Auckett, JE; Avdeev, M; Ling, CDBa 3 Fe 2.15 W 0.85 O 8.72 has been grown as large single crystals using the floating-zone method, permitting very precise characterization of the nuclear and magnetic structures by neutron and synchrotron diffraction methods. The results of our structural investigation are combined with dc and ac magnetization and heat capacity measurements to give an unusually complete and detailed picture of a complex magnetic system. The compound crystallizes in the hexagonal perovskite structure (space group P 6 3 / m m c ) and reveals antiferromagnetic order below T N = 290 K. Frequency-dependent ac susceptibility and the presence of magnetic viscosity suggest the onset of a spin glass component in this material below T f = 60 K. These findings are discussed on the basis of detailed analysis of the crystalo-chemical properties, supported by ab initio (density functional theory) calculations.(c) 2011 IOP Publishing Ltd.
- ItemCombined experimental and computational study of oxide ion conduction dynamics in Sr2Fe2O5 brownmillerite(American Chemical Society, 2013-08-13) Auckett, JE; Studer, AJ; Pellegrini, E; Ollivier, J; Johnson, MR; Schober, H; Miiller, W; Ling, CDWe report a detailed study of the dynamics of oxide ionic conduction in brownmillerite-type Sr2Fe2O5, including lattice anisotropy, based on neutron scattering studies of a large (partially twinned) single crystal in combination with ab initio molecular dynamics simulations. Single-crystal diffraction reveals supercell peaks due to long-range ordering among chains of corner-sharing FeO4 tetrahedra, which disappears on heating above 540 °C due to confined local rotations of tetrahedra. Our simulations show that these rotations are essentially isotropic, but are a precondition for the anisotropic motion that moves oxide ions into the tetrahedral layers from the octahedral layers, which we observe experimentally as a Lorentzian broadening of the quasielastic neutron scattering spectrum. This continual but incoherent movement of oxide ions in turn creates conduction pathways and activates long-range diffusion at the interface between layers, which appears to be largely isotropic in two dimensions, in contrast with previously proposed mechanisms that suggest diffusion occurs preferentially along the c axis.© 2013, American Chemical Society.
- ItemCompeting types of long-range 3d magnetic order in the layered molecular network compounds M(NCO)2(pyz), M - Mn, Re or Co(Australian Institute of Physics, 2005-01-31) Ling, CD; Manson, JLWe have synthesised M(NCO)2(pyz) compounds where M is Mn, Fe or Co. We present the results of a neutron powder diffraction investigation into the crystal and magnetic structures of these compounds as a function of temperature. We find that the structures of all three compounds are isomorphic and related to that of Mn(N3)2(pyz), and yet exhibit two distinct magnetic structures at low temperature. The relationship between these two magnetic structures, and the finely balanced magnetic exchange interactions that lead to the adoption of one over the other, are discussed. © 2005 Australian Institute of Physics
- ItemComplex 5d magnetism in a novel S= 1/2 trimer system, the 12L hexagonal perovskite ba4biir3o12(American Chemical Society, 2013-10-21) Miiller, W; Dunstan, MT; Huang, Z; Mohamed, Z; Kennedy, BJ; Avdeev, M; Ling, CDThe 12L hexagonal perovskite Ba4BiIr3O12 has been synthesized for the first time and characterized using high-resolution neutron and synchrotron X-ray diffraction as well as physical properties measurements. The structure contains Ir3O12 linear face-sharing octahedral trimer units, bridged by corner-sharing BiO6 octahedra. The average electronic configurations of Ir and Bi are shown to be +4(d5) and +4(s1), respectively, the same as for the S = 1/2 dimer system Ba3BiIr2O9, which undergoes a spin-gap opening with a strong magnetoelastic effect at T* = 74 K. Anomalies in magnetic susceptibility, heat capacity, electrical resistivity, and unit cell parameters indeed reveal an analogous effect at T* ≈ 215 K in Ba4BiIr3O12. However, the transition is not accompanied by the opening of a gap in spin excitation spectrum, because antiferromagnetic coupling among S = 1/2 Ir4+ (d5) cations leads to the formation of a S = 1/2 doublet within the trimers, vs S = 0 singlets within dimers. The change in magnetic state of the trimers at T* leads to a structural distortion, the energy of which is overcompensated for by the formation of S = 1/2 doublets. Extending this insight to the dimer system Ba3BiIr2O9 sheds new light on the more pronounced low-temperature anomalies observed for that compound. © 2013, American Chemical Society.
- ItemComplex magnetism of quasi-1D maricite-type NaFePO4(AOCNS 2015, 2015-07-23) Avdeev, M; Piltz, RO; Ling, CD; Auckett, JE; Barpanda, P; Cadogan, JMWe recently reported the magnetic structure of maricite-type NaFePO4 determined using neutron powder diffraction data collected at 3 K1. The crystal structure of this compound is derived from the olivine (Mg2SiO4) type by an ordered distribution of Na and Fe over the two inequivalent Mg sites in the olivine cell. This leads to a magnetically quasi-1D arrangement in which edge-sharing (FeO6) chains are connected to each other only via phosphate groups with a shortest interchain Fe-Fe distance of ~5 Å vs. intrachain distance of ~3.4 Å. Here we report the results of further studies using magnetometry, heat capacity, Mossbauer, and variable field and temperature powder and single crystal neutron diffraction measurements, which reveal not only an intermediate incommensurate magnetic phase existing in zero field within a very narrow interval of ~2 K, but also a metamagnetic transition around 5 T (at 2 K). We will also present and discuss the evolution of the magnetic structure of NaFePO4 as a function of temperature and magnetic field in connection with the crystal structure and compared to that of other maricite type compositions such as AgMnVO42.
- ItemCorrigendum to “Synthesis, structures, and phase transitions of barium bismuth iridium oxide perovskites Ba2BiIrO6 and Ba3BiIr2O9” [J. Solid State Chem. 183 (2010) 727–735](Elsevier, 2010-11-01) Ling, CD; Kennedy, BJ; Zhou, Q; Spencer, JR; Avdeev, MThe authors wish to draw the reader’s attention to an unfortunate series of typographical errors in this article. The space group of Ba2BiIrO6 at room temperature was incorrectly referred to throughout the text as R3 , The correct space group is R3c . which was used for all the Rietveld-refinements and to generate all the relevant tables and figures. © 2010 Elsevier Inc.
- ItemCrystal and magnetic structure of Li2MnSiO4 and Li2CoSiO4 characterized by neutron diffraction measurement(Australian Institute of Physics, 2014-02-06) Mohamed, Z; Avdeev, M; Ling, CDLithium orthosilicates compounds Li2MnSiO4 and Li2CoSiO4 were synthesized by solid state reaction and characterized using X-ray powder diffraction, magnetic susceptibility measurement, heat capacity and neutron powder diffraction. The magnetic susceptibility measurement shows that Li2MnSiO4 and Li2CoSiO4 obey Curie Weiss behaviour at high temperature and undergo antiferromagnetic ordering below TN = ~12 K and ~13 K respectively. The magnetic structures of both compound have been solved for the first time using low temperature neutron diffraction data. The results reveal that the magnetic structure of Li2CoSiO4 can be described as antiferromagnetic quasi-layers stacked along the a-axis with the magnetic moment ~2.92 μB aligned parallel to the a-axis. The magnetic structure of Li2MnSiO4 showed quite different behaviour compared to Li2CoSiO4. The origin of this complex magnetic structures will be discussed in terms of super-superexchange interactions among the transition metal ions, mediated by bridging SiO4 tetrahedra.
- ItemCrystal and magnetic structures of melilite-type Ba2MnSi2O7(American Chemical Society, 2019-03-06) Sale, M; Xia, Q; Avdeev, M; Ling, CDMelilite-type Ba2MnSi2O7 was synthesized by a standard powder solid-state reaction route, and its magnetic properties were studied at low temperature. The magnetic structure was found to be C-type pointing along the c axis from neutron powder diffraction, which is different from the G-type ordering previously reported in all other 2-2-4-2 melilites with manganese as the B′-site transition metal. Ab initio (density functional theory) and magnetic dipole–dipole calculations were used to understand the magnetic structure by determining the spin supersuperexchange parameters as well as the relative influence of spin–orbit coupling and the magnetic dipole–dipole interactions. © 2019 American Chemical Society
- ItemCrystal structure and monoclinic distortion of glaserite-type Ba3MnSi2O8(Elsevier, 2018-10-01) Avdeev, M; Xia, Q; Sale, M; Allison, MC; Ling, CDCrystal structure and magnetic properties of glaserite-type Ba3MnSi2O8 were investigated using variable temperature neutron powder diffraction and magnetometry. At room temperature the composition is hexagonal and the crystal structure is best described by the P-3m1 space group (a~ 5.7 Å, c~ 7.3 Å) with the apical oxygen atom modelled on a split site. On cooling below ~ 250 K the structure undergoes a phase transition into a monoclinic C2/c form (√3ahex, ahex, 2chex, β~ 90°). Analysing diffraction data in terms of symmetry-adapted distortion modes suggests that the transition is primarily driven by increasing in-plane displacements of O1, which in turn results in the coupled tilting of [SiO4] and [MnO6] octahedra and in-plane displacements of Ba1 atoms. Magnetic susceptibility measurements and neutron powder diffraction data show no evidence for long-range magnetic ordering down to 1.6 K, although the development of magnetic diffuse scattering suggests that a magnetic transition may take place at lower temperature. Crown Copyright © 2018 Published by Elsevier Inc.
- ItemCrystal structures of orthorhombic, hexagonal, and cubic compounds of the Sm(x)Yb(2−x)TiO5 series(Elsevier, 2014-05) Aughterson, RD; Lumpkin, GR; Reyes, MDL; Sharma, N; Ling, CD; Gault, B; Smith, KL; Avdeev, M; Cairney, JMA series of single phase compounds with nominal stoichiometry Sm(x)Yb(2−x)TiO5 (x=2, 1.4, 1, 0.6, and 0) have been successfully fabricated to generate a range of crystal structures covering the most common polymorphs previously discovered in the Ln2TiO5 series (Ln=lanthanides and yttrium). Four of the five samples have not been previously fabricated in bulk, single phase form so their crystal structures are refined and detailed using powder synchrotron and single crystal x-ray diffraction, neutron diffraction and transmission electron microscopy. Based on the phase information from diffraction data, there are four crystal structure types in this series; orthorhombic Pnma, hexagonal P63/mmc, cubic (pyrochlore-like) Fd-3m and cubic (fluorite-like) Fm-3m. The cubic materials show modulated structures with variation between long and short range ordering and the variety of diffraction techniques were used to describe these complex crystal structure types. © 2014, Elsevier Inc.
- ItemCu5SbO6 – synchrotron, neutron diffraction studies and magnetic properties(Australian Institute of Physics, 2011-02-04) Söhnel, T; Rey, E; Ling, CD; Avdeev, M; Johannessen, B; Wallwork, KS; Kremer, RK; Whangbo, MHOne very interesting compound in the system Cu/Sb/O is the mixed-valent Cu5SbO6 = (Cu1+(Cu2+ 2/3Sb5+ 1/3)O2) which is crystallising in the high temperature modification as a modified Delafossite structure type. Compounds like Delafossite, CuFeO2, is one of the few groups of compounds showing the rare property of multiferroic behaviour. In Cu5SbO6 the magnetically active brucite-like CuO2 layer is diluted in an ordered fashion with nonmagnetic Sb5+. Cu5SbO6 also shows a phase transition, which exhibits a rather complicated behaviour. It depends on the temperature and the reaction conditions (reactants for preparation, pressure, open or closed system). High resolution Synchrotron and neutron powder diffraction measurements could clearly distinguish between the high temperature and the low temperature modification and reveal an ordering (HT-modification) / disordering (LT-modification) effect of the Sb5+ and Cu2+ ions in the brucite-like layers. The LT-modification can also be assigned to what had wrongly been described in the literature as Cu4.5SbO5. XANES Cu-K edge measurements and NPD measurements should clarify a potential oxidation of the Cu1+ to Cu2+ and a connected additional inclusion of oxygen in the structure. According to magnetic measurements and DFT calculations the magnetic structure in Cu5SbO6 can be described with a short range ferromagnetic-antiferromagnetic interaction model of the (Cu2+) pairs in the (Cu2+ 2/3Sb5+ 1/3)O2 layers with a super-exchange via the nonmagnetic Sb5+ atoms. The systematic replacement of the non-magnetic Sb5+ with magnetically active M5+ ions should change the magnetic properties dramatically and could lead to an long range ordering in the system. First results of Mn and Mo doping will also be presented.
- ItemDesigning new n = 2 Sillen-Aurivillius phases by lattice-matched substitutions in the halide and [Bi2O2]2+ layer(Australian Institute of Physics, 2014-02-05) Liu, S; Blanchard, PER; Kennedy, BJ; Ling, CD; Avdeev, MThe chemical and structural flexibility of the perovskite structure, which makes it so ubiquitous in nature and useful in a range of technological applications, extends to layered variants such as Ruddlesden-Popper, Dion- Jacobson and Aurivillius phases. Multi-layered variants such as the Sillen-Aurivillius phases are related to Aurivillius phases by the insertion of an additional halide layer between every second [Bi2O2]2+ layer. Sillen-Aurivillius phases exist in various combinations of n number of perovskite layers and m halide layers. We have synthesised a new n = 2, m = 1 Sillen-Aurivillius compound Bi3Sr2Nb2O11Br based on Bi3Pb2Nb2O11Cl by simultaneously replacing Pb2+ with Sr2+ and Cl- with Br-. Rietveld refinements against X-ray and neutron powder diffraction data revealed a significant relative compression in the stacking axis, in contrary to the belief of inserting a significantly larger halide layer in the new compound. We could not stabilise other combinations such as Bi3Sr2Nb2O11Cl and Bi3Pb2Nb2O11Br due to inter-layer mismatch. Sr2+ doping reduces the impact of the stereochemically active 6s2 lone pair found on Bi3+/Pb2+ site, resulting in a contraction of the stacking axis by 1.22 % and an expansion of the a-b plane by 0.25 %, improving inter-layer compatibility with Br-. XANES analysis shows that the ferroelectric distortion of the B-site cation is less apparent in Bi3Sr2Nb2O11Br compared to Bi3Pb2Nb2O11Cl. Variable-temperature neutron diffraction data show no evidence for a ferroelectric distortion.
- ItemDesigning new n=2 Sillen-Aurivillius phases by lattice-matched substitutions in the halide and [Bi 2Oc2] 2+ layer(Australian Institute of Nuclear Science and Engineering (AINSE), 2013-12-02) Liu, S; Blanchard, PER; Avdeev, M; Kennedy, BJ; Ling, CDThe chemical and structural flexibility of the perovskite structure, which makes is so ubiquitous in nature and useful in a range of technological applications, extends to layered variants such as Ruddleston-Popper, Dion-Jacobsen and Aurivillius phases. Multi-layered variants such as the Sillen-Aurivillius phases are related to Aurivillius phases by the insertion of an additional halide layer between every second [Bi2 02 2+ layer. Sillen-Aurivillius phases exist in various AnXm combinations, where n is the number of perovskite layers A and m the number of halide layers X. We have synthesised a new n=2 Sillen-Aurivillius compound Bi3 Sr2 Nb2 O11 Br based on Bi3 Pb2 Nb2 O11 Cl by simultaneously replacing Pb2+ with Sr2+ and Cl - with Br -. Rietveld refinements against X-ray and neutron powder diffraction data revealed a significant relative compression in the stacking axis (c axis) in contrary to the belief of inserting a significantly larger halide layer in the new compound. We could not stabilise other combinations such as Bi3 Sr2 Nb2 O11 Cl and Bi3 Pb2 Nb2 O11 Br due to inter-layer mismatch. Sr2+ doping reduces the impact of the stereochemically active 6s2 lone pair found on Pb2+and Bi3+, resulting in a contraction of the c axis by 1.22 % and an expansion of the a-b plane by 0.25 %, improving inter-layer compatibility with Br-. XANES analysis shows that the ferroelectric distortion of the B-site cation is less apparent in Bi3 Sr2 Nb2 O11 Br compared to Bi3 Pb2 Nb2 O11 Cl. Variable-temperature neutron diffraction data show no evidence for a ferroelectric distortion.
- ItemDesigning new n=2 sillen-aurivillius phases by lattice-matched substitutions in the halide and [Bi2O2](2+) layers(Academic Press Inc Elsevier Science, 2013-09-01) Liu, S; Blanchard, PER; Avdeev, M; Kennedy, BJ; Ling, CDAbstract A new n=2 Sillen–Aurivillius compound Bi3Sr2Nb2O11Br has been synthesised based on Bi3Pb2Nb2O11Cl by simultaneously replacing Pb2+ with Sr2+ and Cl− with Br−. Rietveld refinements against X-ray and neutron powder diffraction data revealed a significant relative compression in the stacking axis (c-axis) of the new compound. Sr2+ doping reduces the impact of the stereochemically active 6s2 lone pair found on Pb2+ and Bi3+, resulting in a contraction of the c-axis by 1.22% and an expansion of the ab plane by 0.25%. This improves the inter-layer compatibility with the larger halide Br−. Analysis of X-ray absorption near-edge spectroscopy data show that the ferroelectric distortion of the B-site cation is less apparent in Bi3Sr2Nb2O11Br compared to Bi3Pb2Nb2O11Cl, and variable-temperature neutron diffraction data show no evidence for a ferroelectric distortion.© 2013, Elsevier Inc