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55 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I15-Extreme Conditions	Quasi-hydrostatic equation of state of silicon up to 1 megabar at ambient temperature Simone Anzellini , Michael T. Wharmby , Francesca Miozzi , Annette Kleppe , Dominik Daisenberger , Heribert Wilhelm Scientific Reports 9 DOI: 10.1038/s41598-019-51931-1 Diamond Proposal Number(s): [13527] Open Access Show Abstract ▼ Abstract: The isothermal equation of state of silicon has been determined by synchrotron x-ray diffraction experiments up to 105.2 GPa at room temperature using diamond anvil cells. A He-pressure medium was used to minimize the effect of uniaxial stress on the sample volume and ruby, gold and tungsten pressure gauges were used. Seven different phases of silicon have been observed along the experimental conditions covered in the present study.	Oct 2019
I15-Extreme Conditions	Origin of the large electrostrain in BiFeO 3 -BaTiO 3 based lead-free ceramics Ge Wang , Zhongming Fan , Shunsuke Murakami , Zhilun Lu , David A. Hall , Derek C. Sinclair , Antonio Feteira , Xiaoli Tan , Jacob L. Jones , Annette K. Kleppe , Dawei Wang , Ian M. Reaney Journal Of Materials Chemistry A 21 DOI: 10.1039/C9TA07904A Diamond Proposal Number(s): [19590] Show Abstract ▼ Abstract: High electrostrain and breakdown strength (1 − x)BiFeO3-0.3BaTiO3-xNd(Li0.5Nb0.5)O3 (BF-BT-xNLN) ceramics were studied by in situ synchrotron X-ray diffraction (XRD) in combination with Rietveld refinement and conventional transmission electron microscopy. At zero field, compositions transformed from majority ferroelectric rhombohedral to pseudocubic as the NLN concentration increased, with 0.27% strain achieved at 60 kV cm−1 for x = 0.01. The large measured macroscopic strain was commensurate with peak shifting in XRD peak profiles, yielding 0.6% total strain at 150 kV cm−1. Strain anisotropy of ε200 > ε220 > ε111 was observed but despite the large applied field, no peak splitting was detected. We therefore concluded that the large electrostrain is not achieved through a conventional relaxor to field induced long-range ferroelectric transition. Instead, the data supports a model where local polar regions distort in the direction of the applied field within multiple local symmetries (pseudosymmetry) without long range correlation. We proposed that pseudosymmetry is maintained in BF-BT-xNLN even at high field (150 kV cm−1) due to the large ion radii mismatch and competing ionic/covalent bonding between Ba2+ and Bi3+ ions.	Aug 2019
I15-Extreme Conditions	The effect of pressure and composition on Cu-bearing hydroxide perovskite Jens Najorka , Annette K. Kleppe , Mark D. Welch Physics And Chemistry Of Minerals 36 DOI: 10.1007/s00269-019-01047-9 Diamond Proposal Number(s): [9903, 11121] Open Access Show Abstract ▼ Abstract: Hydroxide perovskite solid solutions along the CuxZn1−xSn(OH)6 join have been investigated at ambient conditions. Two compositions, Cu0.4Zn0.6Sn(OH)6 (cubic) and CuSn(OH)6 (tetragonal), have also been studied at pressures up to 17 GPa. In both ambient and high-pressure experiments, samples were characterised using powder X-ray diffraction. Bulk compositions between 0 ≤ XCu ≤ 0.4 are metrically cubic (space group Pn 3 ¯ 3¯ ), whereas those with XCu = 0.9 and 1 produced single-phase tetragonal Cu0.9Zn0.1Sn(OH)6 and CuSn(OH)6 (space group P42/n). The products of syntheses with 0.5 ≤ XCu ≤ 0.8 contain coexisting cubic and tetragonal phases. The cubic → tetragonal transformation is rationalised in terms of being driven by local strain associated with the accumulation of Cu-rich domains in the cubic phase. The high-pressure studies of cubic Cu0.4Zn0.6Sn(OH)6 and tetragonal CuSn(OH)6 phases showed contrasting behaviour. The compression curve of the cubic phase is smooth without inflexion or discontinuity to 17 GPa. The derived bulk modulus of Cu0.4Zn0.6Sn(OH)6 is K0 = 75.8(4) GPa (K′ = 4). For CuSn(OH)6, compression data cannot be fitted by a single equation-of-state over the entire pressure range to 17 GPa, as there is a clear discontinuity between 7 and 10 GPa that corresponds to an increase in compressibility at higher pressures. Compression data for CuSn(OH)6 to 7 GPa are: K0 = 59.7(9) GPa, Ka0 = 79(2) GPa, and Kc0 = 38.0(3) GPa (K′ = 4 for all). It is shown that the strong Jahn–Teller distortion associated with the Cu(OH)6 octahedron is primarily responsible for the discontinuous and highly anisotropic compressional behaviour of the unit cell of CuSn(OH)6 hydroxide perovskite.	Jul 2019
I15-Extreme Conditions	Quenching-assisted actuation mechanisms in core-shell structured BiFeO3−BaTiO3 piezoceramics Ilkan Calisir , Annette K. Kleppe , Antonio Feteira , David A. Hall Journal Of Materials Chemistry C DOI: 10.1039/C9TC01583C Diamond Proposal Number(s): [16390] Show Abstract ▼ Abstract: Electromechanical actuation in piezoceramics is usually enhanced by creating chemically homogeneous materials with structurally heterogeneous morphotropic phase boundaries, leading to abrupt changes in ion displacement directions within the perovskite unit cell. In the present study, an alternative mechanism to enhance electromechanical coupling is found in both chemically and structurally heterogeneous BiFeO3−BaTiO3 lead-free piezoceramics. Such a mechanism is observed in a composition exhibiting core-shell type microstructure, associated with donor-type substitution of Ti4+ for Fe3+, and is primarily activated by thermal quenching treatment. Here, we describe the use of in-situ high-energy synchrotron X-ray powder diffraction upon the application of a high electric field to directly monitor the ferroelectric and elastic interactions between these composite-like components, formed as core and shell regions within grains. Translational short or long-range ordering is observed in the BiFeO3‒depleted shell regions which undergo significant structural alterations from pseudocubic Pm-3m relaxor-ferroelectric in slow-cooled ceramics to rhombohedral R3c or R3m with long-range ferroelectric order in the quenched state. The strain contributions from each component are calculated, leading to the conclusion that the total macroscopic strain arises predominantly from the transformed shell after quenching. Such observations are also complemented by investigations of microstructure and electrical properties, including ferroelectric behaviour and temperature-dependent dielectric properties.	Jul 2019
I15-Extreme Conditions	Rich polymorphism of a metal-organic framework in pressure-temperature space Remo N. Widmer , Giulio I. Lampronti , Siwar Chibani , Craig Wilson , Simone Anzellini , Stefan Farsang , Annette K. Kleppe , Nicola P. M. Casati , Simon Macleod , Simon A. T. Redfern , François-xavier Coudert , Thomas D. Bennett Journal Of The American Chemical Society DOI: 10.1021/jacs.9b03234 Diamond Proposal Number(s): [19046] Show Abstract ▼ Abstract: We present an in-situ powder X-ray diffraction study on the phase stability and polymorphism of the metal-organic framework ZIF-4, Zn(Imidazolate)2, at simultaneous high-pressure and high-temperature, up to 8 GPa and 600 °C. The resulting pressure-temperature phase diagram reveals four, previously unknown, high-pressure-temperature ZIF phases. The crystal structures of two new phases – ZIF-4-cp-II and ZIF-hPT-II – were solved by powder diffraction methods. The total energy of ZIF-4-cp-II was evaluated using density functional theory calculations and was found to lie in between that of ZIF-4 and the most thermodynamically stable polymorph, ZIF-zni. ZIF-hPT-II was found to possess a doubly-interpenetrated diamondoid-topology and is isostructural with previously reported Cd(Imidazolate)2 and Hg(Imidazolate)2 phases. This phase exhibited extreme resistance to both temperature and pressure. The other two new phases could be assigned with a unit cell and space group, though their structures remain unknown. The pressure-temperature phase diagram of ZIF-4 is strikingly complicated when compared with that of the previously investigated, closely related ZIF-62, and demonstrates the ability to traverse complex energy landscapes of metal-organic systems using the combined application of pressure and temperature.	May 2019
I15-Extreme Conditions	High-pressure crystallisation studies of biodiesel and methyl stearate X. Liu , C. L. Bull , A. K. Kleppe , P. J. Dowding , K. Lewtas , C. R. Pulham Crystengcomm 16 DOI: 10.1039/C9CE00393B Diamond Proposal Number(s): [12840] Show Abstract ▼ Abstract: The widespread use of biodiesel as a renewable fuel offers many potential advantages, but at the same time presents challenges for modern internal combustion engines, particularly for those that involve high-pressure injection of fuel into the combustion chamber. At the typical elevated pressures used in such engines, biodiesel can crystallise and block fuel filters and injection nozzles, thereby causing engine failure. In this study, optical studies and Raman spectroscopy of a typical biodiesel sample contained in a diamond-anvil cell show that biodiesel initially crystallises at ca. 0.2 GPa and then undergoes a series of structural changes on further increase of pressure. On account of the complex composition of biodiesel, this study focused on one of its main components – methyl stearate. Using a combination of Raman spectroscopy, X-ray powder diffraction and neutron powder diffraction, it was shown that methyl stearate exhibits rich polymorphic behaviour when subjected to elevated pressures up to 6.3 GPa. Under non-hydrostatic conditions, pressures as low as 0.1 GPa converted Form V to crystallites of Form III that typically adopt plate-like morphologies. This observation has implications for the pressure-induced crystallisation of biodiesel containing high proportions of methyl stearate because of the potentially serious consequences for blocking of injection nozzles in engines. Four phase transitions over the pressure range of 0.1 GPa to 6.3 GPa were also observed. Form III was recovered on decompression to ambient pressure. High-pressure neutron powder diffraction studies of a perdeuterated sample showed that Form V persisted up to 3.11 GPa. This contrast in behaviour between the X-ray and neutron studies may be a consequence of deuteration, or of compression under non-hydrostatic versus hydrostatic conditions.	Apr 2019
I15-Extreme Conditions	The fate of carbonate in oceanic crust subducted into earth's lower mantle James W. E. Drewitt , Michael J. Walter , Hongluo Zhang , Sorcha C. Mcmahon , David Edwards , Benedict J. Heinen , Oliver T. Lord , Simone Anzellini , Annette K. Kleppe Earth And Planetary Science Letters 511, 213 - 222 DOI: 10.1016/j.epsl.2019.01.041 Diamond Proposal Number(s): [10617, 11896, 15288, 17994] Show Abstract ▼ Abstract: We report on laser-heated diamond anvil cell (LHDAC) experiments in the FeO–MgO–SiO2–CO2 (FMSC) and CaO–MgO–SiO2–CO2 (CMSC) systems at lower mantle pressures designed to test for decarbonation and diamond forming reactions. Sub-solidus phase relations based on synthesis experiments are reported in the pressure range of ∼35 to 90 GPa at temperatures of ∼1600 to 2200 K. Ternary bulk compositions comprised of mixtures of carbonate and silica are constructed such that decarbonation reactions produce non-ternary phases (e.g. bridgmanite, Ca-perovskite, diamond, CO2–V), and synchrotron X-ray diffraction and micro-Raman spectroscopy are used to identify the appearance of reaction products. We find that carbonate phases in these two systems react with silica to form bridgmanite ±Ca-perovskite + CO2 at pressures in the range of ∼40 to 70 GPa and 1600 to 1900 K in decarbonation reactions with negative Clapeyron slopes. Our results show that decarbonation reactions form an impenetrable barrier to subduction of carbonate in oceanic crust to depths in the mantle greater than ∼1500 km. We also identify carbonate and CO2–V dissociation reactions that form diamond plus oxygen. On the basis of the observed decarbonation reactions we predict that the ultimate fate of carbonate in oceanic crust subducted into the deep lower mantle is in the form of refractory diamond in the deepest lower mantle along a slab geotherm and throughout the lower mantle along a mantle geotherm. Diamond produced in oceanic crust by subsolidus decarbonation is refractory and immobile and can be stored at the base of the mantle over long timescales, potentially returning to the surface in OIB magmas associated with deep mantle plumes.	Apr 2019
I15-Extreme Conditions	Pressure promoted low-temperature melting of metal–organic frameworks Remo N. Widmer , Giulio I. Lampronti , Simone Anzellini , Romain Gaillac , Stefan Farsang , Chao Zhou , Ana M. Belenguer , Craig Wilson , Hannah Palmer , Annette K. Kleppe , Michael T. Wharmby , Xiao Yu , Seth M. Cohen , Shane G. Telfer , Simon A. T. Redfern , François-xavier Coudert , Simon Macleod , Thomas Bennett Nature Materials 18, 370 - 376 DOI: 10.1038/s41563-019-0317-4 Diamond Proposal Number(s): [16133, 19046] Show Abstract ▼ Abstract: Metal–organic frameworks (MOFs) are microporous materials with huge potential for chemical processes. Structural collapse at high pressure, and transitions to liquid states at high temperature, have recently been observed in the zeolitic imidazolate framework (ZIF) family of MOFs. Here, we show that simultaneous high-pressure and high-temperature conditions result in complex behaviour in ZIF-62 and ZIF-4, with distinct high- and low-density amorphous phases occurring over different regions of the pressure–temperature phase diagram. In situ powder X-ray diffraction, Raman spectroscopy and optical microscopy reveal that the stability of the liquid MOF state expands substantially towards lower temperatures at intermediate, industrially achievable pressures and first-principles molecular dynamics show that softening of the framework coordination with pressure makes melting thermodynamically easier. Furthermore, the MOF glass formed by melt quenching the high-temperature liquid possesses permanent, accessible porosity. Our results thus imply a route to the synthesis of functional MOF glasses at low temperatures, avoiding decomposition on heating at ambient pressure.	Mar 2019
I15-Extreme Conditions	In-situ XRD study of actuation mechanisms in BiFeO3-K0.5Bi0.5TiO3-PbTiO3 ceramics Yizhe Li , Ying Chen , Zhenbo Zhang , Annette Kleppe , David A. Hall Acta Materialia DOI: 10.1016/j.actamat.2019.02.026 Diamond Proposal Number(s): [16390] Show Abstract ▼ Abstract: In the present study, we report a nonergodic relaxor ferroelectric composition for high temperature piezoelectric applications, 0.57BiFeO3-0.21K0.5Bi0.5TiO3-0.22PbTiO3, which exhibits Tm around 420 °C. By combining the results of in-situ synchrotron XRD and strain measurements using digital image correlation, a pseudocubic nonergodic relaxor to rhombohedral ferroelectric transformation is identified, accompanied by a volume strain close to zero. A methodology is developed to determine the crystallographic parameters of the transformed rhombohedral ferroelectric phase in a strain-free state, using the invariant intersection for diffraction stress analysis. The phase transformation process was analyzed by methods combining peak profile fitting and full pattern refinement; the results obtained illustrate the strain arising from the phase transformation, together with intrinsic/extrinsic contributions and anisotropy in the field-induced strain. The study reveals unusual microscopic strain behavior, distinguished from that of normal rhombohedral ferroelectrics, showing the combined properties of ergodic and normal ferroelectric materials and leading to a dominant intrinsic lattice strain together with a weaker extrinsic domain switching effect. The elastic coupling between different grain families is also reflected in their similar strain orientation distribution (SOD) functions.	Feb 2019
I15-Extreme Conditions	Residual strain mapping through pair distribution function analysis of the porcelain veneer within a yttria partially stabilised zirconia dental prosthesis Alexander J. G. Lunt , Philip Chater , Annette Kleppe , Nikolaos Baimpas , Tee K. Neo , Alexander M. Korsunsky Dental Materials DOI: 10.1016/j.dental.2018.11.013 Diamond Proposal Number(s): [9106] Show Abstract ▼ Abstract: Objective. Residually strained porcelain is influential in the early onset of failure in Yttria Partially Stabilised Zirconia (YPSZ) – porcelain dental prosthesis. In order to improve current understanding it is necessary to increase the spatial resolution of residual strain analysis in these veneers. Methods. Few techniques exist which can resolve residual stress in amorphous materials at the microscale resolution required. For this reason, recent developments in Pair Distribution Function (PDF) analysis of X-ray diffraction data of dental porcelain have been exploited. This approach has facilitated high-resolution (70 μm) quantification of residual strain in a YPSZ-porcelain dental prosthesis. In order to cross-validate this technique, the sequential ring-core focused ion beam and digital image correlation approach was implemented at a step size of 50 μm. This semi-destructive technique exploits microscale strain relief to provide quantitative estimates of the near-surface residual strain. Results. The two techniques were found to show highly comparable results. The residual strain within the veneer was found to be primarily tensile, with the highest magnitude stresses located at the YPSZ-porcelain interface where failure is known to originate. Oscillatory tensile and compressive stresses were also found in a direction parallel to the interface, likely to be induced by the multiple layering used during fabrication. Significance. This study provides the insights required to improve prosthesis modelling, to develop new processing routes that minimise residual stress and ultimately to reduce prosthesis failure rates. The PDF approach also offers a powerful new technique for microscale strain quantification in amorphous materials.	Nov 2018

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