I11-High Resolution Powder Diffraction
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Bernhard T.
Leube
,
Christopher M.
Collins
,
Luke M.
Daniels
,
Benjamin B.
Duff
,
Yun
Dang
,
Ruiyong
Chen
,
Michael W.
Gaultois
,
Troy D.
Manning
,
Frédéric
Blanc
,
Matthew S.
Dyer
,
John B.
Claridge
,
Matthew J.
Rosseinsky
Diamond Proposal Number(s):
[17193]
Open Access
Abstract: A tetragonal argyrodite with >7 mobile cations, Li7Zn0.5SiS6, is experimentally realized for the first time through solid state synthesis and exploration of the Li–Zn–Si–S phase diagram. The crystal structure of Li7Zn0.5SiS6 was solved ab initio from high-resolution X-ray and neutron powder diffraction data and supported by solid-state NMR. Li7Zn0.5SiS6 adopts a tetragonal I4 structure at room temperature with ordered Li and Zn positions and undergoes a transition above 411.1 K to a higher symmetry disordered F43m structure more typical of Li-containing argyrodites. Simultaneous occupation of four types of Li site (T5, T5a, T2, T4) at high temperature and five types of Li site (T5, T2, T4, T1, and a new trigonal planar T2a position) at room temperature is observed. This combination of sites forms interconnected Li pathways driven by the incorporation of Zn2+ into the Li sublattice and enables a range of possible jump processes. Zn2+ occupies the 48h T5 site in the high-temperature F43m structure, and a unique ordering pattern emerges in which only a subset of these T5 sites are occupied at room temperature in I4 Li7Zn0.5SiS6. The ionic conductivity, examined via AC impedance spectroscopy and VT-NMR, is 1.0(2) × 10–7 S cm–1 at room temperature and 4.3(4) × 10–4 S cm–1 at 503 K. The transition between the ordered I4 and disordered F43m structures is associated with a dramatic decrease in activation energy to 0.34(1) eV above 411 K. The incorporation of a small amount of Zn2+ exercises dramatic control of Li order in Li7Zn0.5SiS6 yielding a previously unseen distribution of Li sites, expanding our understanding of structure–property relationships in argyrodite materials.
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Apr 2022
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I11-High Resolution Powder Diffraction
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Dingyue
Hu
,
Karl
Dawson
,
Marco
Zanella
,
Troy D.
Manning
,
Luke M.
Daniels
,
Nigel D.
Browning
,
B. Layla
Mehdi
,
Yaobin
Xu
,
Houari
Amari
,
J. Felix
Shin
,
Michael J.
Pitcher
,
Ruiyong
Chen
,
Hongjun
Niu
,
Bowen
Liu
,
Matthew
Bilton
,
Junyoung
Kim
,
John B.
Claridge
,
Matthew J.
Rosseinsky
Diamond Proposal Number(s):
[23666]
Open Access
Abstract: Performance durability is one of the essential requirements for solid oxide fuel cell materials operating in the intermediate temperature range (500–700 °C). The trade-off between desirable catalytic activity and long-term stability challenges the development and commercialization of electrode materials. Here an oxygen cathode material, Ba0.5Sr0.5(Co0.7Fe0.3)0.69−xMgxW0.31O3−δ (BSCFW-xMg), that exhibits excellent electrocatalytic performance through the addition of an optimized amount of Mg to the self-assembled nanocomposite Ba0.5Sr0.5(Co0.7Fe0.3)0.69W0.31O3−δ (BSCFW) by simple solid-state reaction is reported. Distinct from the bulk and surface approaches to introduce vacancies and defects in materials design, here the Mg2+ ions concentrate at the single perovskite/double perovskite interface of BSCFW with dislocations and Mg2+-rich nanolayers, resulting in stressed and compositionally inhomogeneous interface regions. The interfacial chemistry within these nanocomposites provides an additional degree of freedom to enable performance optimization over single phase materials and promotes the durability of alkaline-earth based fuel cell materials.
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Mar 2022
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I11-High Resolution Powder Diffraction
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Open Access
Abstract: Protonic ceramic fuel cells (PCFCs) are attractive energy conversion devices for intermediate-temperature operation (400-600 °C), however widespread application of PCFCs relies on the development of new high-performance electrode materials. Here we report the electrochemical and protonic properties of a self-assembled nanocomposite, Ba0.5Sr0.5(Co0.7Fe0.3)0.6875W0.3125O3−δ (BSCFW) consisting of a disordered single perovskite and an ordered double perovskite phase, as a PCFC cathode material. BSCFW shows thermodynamic and kinetic protonic behaviour conducive to PCFC application with favourable proton defect formation enthalpy (ΔH = -35±7 kJ mol–1) comparable to existing proton conducting electrolyte materials. BSCFW presents an excellent polarization resistance (Rp) of 0.172(2) Ω cm2 at 600 °C and a high power density of 582(1) mW cm–2 through singlecell measurement, which is comparable performance to current state-of-the-art cathode materials. BSCFW exhibits good chemical and thermal stability against BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) electrolyte with a low Rp degradation rate of 1.0(1) × 10-6 Ω cm2 min-1. These performance and stability figures represent an advance beyond those of Ba0.5Sr0.5Co0.7Fe0.3O3−δ (BSCF), which is unstable under the same conditions and is incompatible with the electrolyte material. Our comprehensive characterization of the protonic properties of BSCFW, whose performance and stability are ensured via the interplay of the single and double perovskite phases, provides fundamental understanding that will inform the future design of high-performance PCFC cathodes.
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Dec 2021
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I11-High Resolution Powder Diffraction
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Harry C.
Sansom
,
Leonardo R. V.
Buizza
,
Marco
Zanella
,
James T.
Gibbon
,
Michael
Pitcher
,
Matthew S.
Dyer
,
Troy D.
Manning
,
Vinod R.
Dhanak
,
Laura M.
Herz
,
Henry J.
Snaith
,
John B.
Claridge
,
Matthew J.
Rosseinsky
Open Access
Abstract: A newly reported compound, CuAgBiI5, is synthesized as powder, crystals, and thin films. The structure consists of a 3D octahedral Ag+/Bi3+ network as in spinel, but occupancy of the tetrahedral interstitials by Cu+ differs from those in spinel. The 3D octahedral network of CuAgBiI5 allows us to identify a relationship between octahedral site occupancy (composition) and octahedral motif (structure) across the whole CuI–AgI–BiI3 phase field, giving the ability to chemically control structural dimensionality. To investigate composition–structure–property relationships, we compare the basic optoelectronic properties of CuAgBiI5 with those of Cu2AgBiI6 (which has a 2D octahedral network) and reveal a surprisingly low sensitivity to the dimensionality of the octahedral network. The absorption onset of CuAgBiI5 (2.02 eV) barely changes compared with that of Cu2AgBiI6 (2.06 eV) indicating no obvious signs of an increase in charge confinement. Such behavior contrasts with that for lead halide perovskites which show clear confinement effects upon lowering dimensionality of the octahedral network from 3D to 2D. Changes in photoluminescence spectra and lifetimes between the two compounds mostly derive from the difference in extrinsic defect densities rather than intrinsic effects. While both materials show good stability, bulk CuAgBiI5 powder samples are found to be more sensitive to degradation under solar irradiation compared to Cu2AgBiI6.
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Nov 2021
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I11-High Resolution Powder Diffraction
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Christopher M.
Collins
,
Luke M.
Daniels
,
Quinn
Gibson
,
Michael W.
Gaultois
,
Michael
Moran
,
Richard
Feetham
,
Michael J.
Pitcher
,
Matthew S
Dyer
,
Charlene
Delacotte
,
Marco
Zanella
,
Claire A.
Murray
,
Gyorgyi
Glodan
,
Olivier
Perez
,
Denis
Pelloquin
,
Troy D.
Manning
,
Jonathan
Alaria
,
George R.
Darling
,
John B.
Claridge
,
Matthew J.
Rosseinsky
Open Access
Abstract: We report the aperiodic titanate Ba 10 Y 6 Ti 4 O 27 with a room temperature thermal conductivity that equals the lowest reported for an oxide. The structure is characterised by discontinuous occupancy modulation of each of the sites, and can be considered as a quasicrystal. The resulting localisation of lattice vibrations suppresses phonon transport of heat. This new lead material for low thermal conductivity oxides is metastable and located within a quaternary phase field that has been previously explored – its isolation thus requires a precisely‐defined synthetic protocol. The necessary narrowing of the search space for experimental investigation is achieved by evaluation of titanate crystal chemistry, prediction of unexplored structural motifs that will favour synthetically accessible new compositions and assessment of their properties with machine learning models.
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May 2021
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I11-High Resolution Powder Diffraction
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Luis
Alvarado Rupflin
,
Hendrik
Van Rensburg
,
Marco
Zanella
,
Elliot J.
Carrington
,
Rebecca
Vismara
,
Alexios
Grigoropoulos
,
Troy D.
Manning
,
John B.
Claridge
,
Alexandros P.
Katsoulidis
,
Robert P.
Tooze
,
Matthew J.
Rosseinsky
Abstract: A proxy-based high-throughput experimental approach was used to explore the stability and activity of Co-based Fischer-Tropsch Synthesis catalysts with different promoters on a variety of supports. The protocol is based on XRD estimation of the active phase polymorph, particle size and ratio of crystalline phases of Co to support. Sequential sample libraries enabled exploration of four Co loadings with five different promoters on six support materials. Catalysts stable to aging in syngas, i.e. displaying minimal change of particle size or active phase concentration, were evaluated under industrial conditions. This procedure identified SiC as a support that confers catalyst stability and that a combination of Ru and Hf promotes the stabilisation of hcp Co. Unsupported bulk samples of Co with appropriate amounts of Ru and Hf revealed that the formation of hcp Co is independent of the support. The hcp Co-containing catalyst afforded the highest catalytic activity and C5+ selectivity amongst the samples tested in this study, confirming the effectiveness of the proxy-based high-throughput method.
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Mar 2021
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I11-High Resolution Powder Diffraction
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Craig I.
Hiley
,
Kenneth K.
Inglis
,
Marco
Zanella
,
Jiliang
Zhang
,
Troy D.
Manning
,
Matthew S.
Dyer
,
Tilen
Knaflič
,
Denis
Arčon
,
Frédéric
Blanc
,
Kosmas
Prassides
,
Matthew J.
Rosseinsky
Open Access
Abstract: The products of the solid-state reactions between potassium metal and tetracene (K:Tetracene, 1:1, 1.5:1, and 2:1) are fully structurally characterized. Synchrotron X-ray powder diffraction shows that only K2Tetracene forms under the reaction conditions studied, with unreacted tetracene always present for x < 2. Diffraction and 13C MAS NMR show that K2Tetracene has a crystal structure that is analogous to that of K2Pentacene, but with the cations ordered on two sites because of the influence of the length of the hydrocarbon on possible cation positions. K2Tetracene is a nonmagnetic insulator, thus further questioning the nature of reported superconductivity in this class of materials.
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Aug 2020
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I11-High Resolution Powder Diffraction
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Open Access
Abstract: 6,6′,13,13′- tetrahydro-6,6′-bipentacene (HBP), the intermediate molecule connecting pentacene to previously observed peripentacene and extended pentacene oligomers through the formation of a carbon-carbon bond, is synthesised and crystallographically characterised. Heating pentacene to 300 ºC under vacuum for 200 hours results in pale golden crystals of HBP and amorphous material containing pentacene oligomers, offering experimental evidence that pentacene preferentially dimerises at the 6,6′- position. Continued heating of HBP results in co-crystals of 6,13-dihydrogenated pentacene (HP) and pentacene and further amorphous pentacene oligomers. The amorphous material consists of layered carbonaceous species with a graphenic nature, as determined by Raman spectroscopy and electron microscopy, and suggests HBP as an intermediate to hydrogenated pentacene species and pentacene oligomers, such as peripentacene, of interest in organic electronics.
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Jun 2019
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I11-High Resolution Powder Diffraction
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Abstract: We present the synthesis and characterization of the K+ intercalated rubrene (C42H28) phase, K2Rubrene (K2R) and identify the co-existence of amorphous and crystalline materials in samples where the crystalline component is phase pure. We suggest this is characteristic of many intercalated alkali metal-polyaromatic hydrocarbon (PAH) systems, including those for which superconductivity has been claimed. The systematic investigation of K-rubrene solid state reactions using both K and KH sources reveals complex competition between K intercalation and the decomposition of rubrene, producing three K-intercalated compounds, namely, K2R, K(RR*), and KxRʹ (where R* and Rʹ are rubrene decomposition derivatives C42H26 and C30H20, respectively). K2R is obtained as the major phase over a wide composition range and is accompanied by the formation of amorphous by-products from the decomposition of rubrene. K(RR*) is synthesized as a single phase and KxRʹ is obtained only as a secondary phase to the majority K2R phase. The crystal structure of K2R was determined using high resolution powder X-ray diffraction, revealing that the structural rearrangement from pristine rubrene creates two large voids per rubrene within the molecular layers in which K+ is incorporated. K+ cations accommodated within the large voids interact strongly with the neighbouring rubrene via η6, η3 and η2 binding modes to the tetracene cores and the phenyl groups. This contrasts with other intercalated PAHs where only a single void per PAH is created and the intercalated K+ weakly interact with the host. The decomposition products of rubrene are also examined using solution NMR, highlighting the role of the breaking of C-CPhenyl bonds. For the crystalline decomposition derivative products K(RR*) and KxRʹ, a lack of definitive structural information with regards to R* and Rʹ prevents the crystal structures being determined. The study illustrates the complexity in accessing solvent-free alkali metal salts of reduced PAH of the type claimed to afford superconductivity.
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Nov 2018
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I11-High Resolution Powder Diffraction
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Bernhard T.
Leube
,
Kenneth K.
Inglis
,
Elliot
Carrington
,
Paul M.
Sharp
,
J. Felix
Shin
,
Alex R.
Neale
,
Troy D.
Manning
,
Michael J.
Pitcher
,
Laurence
Hardwick
,
Matthew S.
Dyer
,
Frédéric
Blanc
,
John B.
Claridge
,
Matthew J.
Rosseinsky
Open Access
Abstract: In order to understand the structural and compositional factors controlling lithium transport in sulfides, we explored the Li5AlS4 – Li4GeS4 phase field for new materials. Both parent compounds are defined structurally by a hexagonal close packed sulfide lattice, where distinct arrangements of tetrahedral metal sites give Li5AlS4 a layered structure and Li4GeS4 a three dimensional structure related to γ-Li3PO4. The combination of the two distinct structural motifs is expected to lead to new structural chemistry. We identified the new crystalline phase Li4.4Al0.4Ge0.6S4, and investigated the structure and Li+ ion dynamics of the family of structurally related materials Li4.4M0.4M’0.6S4 (M = Al3+, Ga3+ and M’= Ge4+, Sn4+). We used neutron diffraction to solve the full structures of the Al-homologues, which adopt a layered close-packed structure with a new arrangement of tetrahedral (M/M’) sites and a novel combination of ordered and disordered lithium vacancies. AC impedance spectroscopy revealed lithium conductivities in the range 3(2) x 10-6 to 4.3(3) x 10-5 S cm-1 at room temperature with activation energies between 0.43(1) and 0.38(1) eV. Electrochemical performance was tested in a plating and stripping experiment against Li metal electrodes and showed good stability of the Li4.4Al0.4Ge0.6S4 phase over 200 hours. A combination of variable temperature 7Li solid state nuclear magnetic resonance spectroscopy and ab initio molecular dynamics calculations on selected phases showed that two dimensional diffusion with a low energy barrier of 0.17 eV is responsible for long-range lithium transport, with diffusion pathways mediated by the disordered vacancies while the ordered vacancies do not contribute to the conductivity. This new structural family of sulfide Li+ ion conductors offers insight into the role of disordered vacancies on Li+ ion conductivity mechanisms in hexagonally close packed sulfides that can inform future materials design.
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Sep 2018
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