I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[21686]
Abstract: Li1+xAlxGe2-x(PO4)3 (LAGP) thin films have been grown on sapphire substrates by RF magnetron sputtering and post annealing. The effects of varying sputtering parameters such as power and pressure were studied, and the deposited films were characterized to investigate how the ionic conductivity values depend on the microstructure. The composition of as-sputtered films was found to be more strongly influenced by power than the pressure. The films deposited at lower powers, which results in lower deposition rates, have compositions similar to that of the target. Heating the substrates during deposition is found to minimise the formation of pinhole defects in films subsequently annealed at higher temperatures. Post annealing leads to a gradual transformation from the as-sputtered amorphous phase to crystalline LAGP thin films. At high annealing temperatures (above 700 °C) both porosity and the GeO2 impurity phase appear in the films and result in lower ionic conductivities. We have optimised the processing conditions to achieve ionic conductivities in excess of 10−4 Scm−1 and activation energies as low as 0.31 eV in films only 1 μm thick, suggesting that LAGP could offer attractive properties as a thin film battery electrolyte material.
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Oct 2020
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[17716]
Abstract: Six industrial clinker samples, produced using petroleum coke as kiln fuel, were analysed using high resolution synchrotron XRPD data, one sample (HM) presenting predominantly M1 C3S polymorph. Refinement of data collected on this sample was used to revise the M1 structural model, improving the Rwp and RB of the original model (from Rwp = 9.25 and RB = 5.517 in the original model to Rwp = 8.07 and RB = 2.965). The revised model was validated through bond length and Bond Valence Sum (BVS) distribution. Using the BVS method, two preferential substitutional calcium sites were identified for Mg2+ and two silicon sites for Al3+, while two interstitial sites were identified for S6+ and Fe3+. Using the revised model for refinement of the six industrial clinker samples showed improvement in the Rwp and GoF indices. The amount of M1 and M3 polymorph present was found to be significantly different using the revised M1 C3S model.
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Oct 2020
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[13284]
Abstract: Topochemical reduction of the n = 1 Ruddlesden–Popper phases LaSrCo0.5Rh0.5O4 and LaSrNi0.5Rh0.5O4 with Zr yields LaSrCo0.5Rh0.5O3.25 and LaSrNi0.5Rh0.5O3.25, respectively. Magnetization and XPS data reveal that while the rhodium centers in LaSrCo0.5Rh0.5O3.25 and LaSrNi0.5Rh0.5O3.25 have an average oxidation state of Rh2+, these are actually mixed valence Rh(I,III) compounds, with the disproportionation of Rh2+ driven by the favorability of locating d8 Rh1+ and d6 Rh3+ cations within square-planar and square-based pyramidal coordination sites, respectively.
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Sep 2020
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[21726, 23666]
Abstract: Three-dimensional (3D) covalent organic frameworks (COFs) are rare because there is a limited choice of organic building blocks that offer multiple reactive sites in a polyhedral geometry. Here, we synthesized an organic cage molecule (cage-6-NH2), which was used as a triangular prism node to yield the first cage-based 3D COF, 3D-CageCOF-1. This COF adopts an unreported twofold interpenetrated acs topology and exhibits reversible dynamic behavior, switching between a small-pore (sp) structure and a large-pore (lp) structure. It also shows high CO2 uptake and captures water at low humidity (<40%). This demonstrates the potential for expanding the structural complexity of 3D COFs by using organic cages as the building units.
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Sep 2020
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[13284]
Open Access
Abstract: Synchrotron X-ray powder diffraction data indicate that La0.5Sr0.5Mn0.5Rh0.5O3 and La0.5Sr0.5Fe0.5Rh0.5O3 adopt distorted perovskite structures (space group Pnma) with A-site and B-site cation disorder. A combination of XPS and 57Fe Mössbauer data indicate the transition metal cations in the two phases adopt Mn3+/Rh4+ and Fe3+/Rh4+ oxidation state combinations respectively. Transport data indicate both phases are insulating, with ρ vs. T dependences consistent with 3D variable-range hopping. Magnetisation data reveal that La0.5Sr0.5Mn0.5Rh0.5O3 adopts a ferromagnetic state below Tc ∼ 60 K, which is rationalized on the basis of coupling via a dynamic Jahn–Teller distortion mechanism. In contrast, magnetic data reveal La0.5Sr0.5Fe0.5Rh0.5O3 undergoes a transition to a spin-glass state at T ∼ 45 K, attributed to frustration between nearest-neighbour Fe–Rh and next-nearest-neighbour Fe–Fe couplings.
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Aug 2020
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[14809]
Abstract: Potassium-ion batteries (KIB) are a promising complementary technology to lithium-ion batteries because of the comparative abundance and affordability of potassium. Currently, the most promising KIB chemistry consists of a potassium manganese hexacyanoferrate (KMF) cathode, a Prussian blue analog, and a graphite anode (723Whl−1 and 359Whkg−1 at 3.6V). No electrolyte has yet been formulated that is concurrently stable at the high operating potential of KMF (4.02V vs K+/K) and compatible with K+ intercalation into graphite, currently the most critical hurdle to adoption. Here we combine a KMF cathode and a graphite anode with a KFSI in Pyr1,3FSI ionic liquid electrolyte for the first time and show unprecedented performance. We use high-throughput techniques to optimize the KMF morphology for operation in this electrolyte system, achieving 119 mA h g−1 at 4 V vs K+/K and a coulombic efficiency >99.3%. In the same ionic liquid electrolyte graphite shows excellent electrochemical performance and we demonstrate reversible cycling by operando XRD. These results are a significant and essential step forward towards viable potassium-ion batteries.
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Aug 2020
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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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Diamond Proposal Number(s):
[13284]
Abstract: Na-for-Rb cation exchange followed by K-for-Na cation exchange of RbNdM2O7 (M = Nb, Ta) yields the corresponding, metasta-ble KNdM2O7 phases. Synchrotron X-ray and neutron powder diffraction data, combined with powder SHG data, reveal that the KNdM2O7 phases adopt a polar structure (space group Im2m) consisting of NdM2O7 double perovskite sheets stacked in a (0, ½, z) manner with K+ cations ordered within the 6-coordinate prismatic inter-layer sites. The perovskite double sheets adopt an (a0b+c0/a0-b+c0) tilting distortion, however unlike other A’AB2O7 phases this distortion is not the origin of the non-centrosymmetric structure, which is attributed to a second-order Jahn-Teller distortion of the MO6 units. First-principles DFT calculations confirm the polar Im2m phase is more stable than the corresponding centrosymmetric alternative. The role of the A’- and A- cations in di-recting the stacking patterns and tilting distortions of A’AB2O7 phases is discussed with reference to hybrid improper ferroelectric behavior.
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Aug 2020
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[14555]
Open Access
Abstract: Temperature or pressure-swing sorption in porous metal-organic framework (MOF) materials has been proposed for new gas separation technologies. The high tuneability of MOFs toward particular adsorbates and the relatively low energy penalty for system regeneration means that reversible physisorption in MOFs has the potential to create economic and environmental benefits compared with state-of-the-art chemisorption systems. However, for MOF-based sorbents to be commercialised they have to show long-term stability under the conditions imposed by the application. Here, we demonstrate the structural stability of MFM-300(Al) to the presence of a series of industrially-relevant toxic and corrosive gases, including SO2, NO2 and NH3, over four years using long duration synchrotron X-ray powder diffraction. Full structural analysis of gas-loaded MFM-300(Al) confirms the retention of these toxic gas molecules within the porous framework for up to 200 weeks, and cycling adsorption experiments verified the reusability of MFM-300(Al) for the capture of these toxic air pollutants.
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Aug 2020
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B22-Multimode InfraRed imaging And Microspectroscopy
I11-High Resolution Powder Diffraction
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Xiaolin
Li
,
Juehua
Wang
,
Xinran
Zhang
,
Xue
Han
,
Ivan
Da Silva
,
Christopher G.
Morris
,
Shaojun
Xu
,
Damian M.
Wilary
,
Yinyong
Sun
,
Yongqiang
Cheng
,
Claire A.
Murray
,
Chiu C.
Tang
,
Mark D.
Frogley
,
Gianfelice
Cinque
,
Tristan
Lowe
,
Haifei
Zhang
,
Anibal J.
Ramirez-cuesta
,
K. Mark
Thomas
,
Leslie W.
Bolton
,
Sihai
Yang
,
Martin
Schroeder
,
Nannan
Bai
Diamond Proposal Number(s):
[13247]
Open Access
Abstract: The demand for xylenes is projected to increase over the coming decades. The separation of xylene isomers, particularly p- and m-xylenes, is vital for the production of numerous polymers and materials. However, current state-of-the-art separation is based upon fractional crystallisation at 220 K which is highly energy intensive. Here, we report the discrimination of xylene isomers via refinement of the pore size in a series of porous metal–organic frameworks, MFM-300, at sub-angstrom precision leading to the optimal kinetic separation of all three xylene isomers at room temperature. The exceptional performance of MFM-300 for xylene separation is confirmed by dynamic ternary breakthrough experiments. In-depth structural and vibrational investigations using synchrotron X-ray diffraction and terahertz spectroscopy define the underlying host–guest interactions that give rise to the observed selectivity (p-xylene < o-xylene < m-xylene) and separation factors of 4.6–18 for p- and m-xylenes.
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Aug 2020
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