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64 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6, 7 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I15-Extreme Conditions	Actuation mechanisms in mixed-phase K0.5Bi0.5TiO3-BiFeO3-PbTiO3 ceramics Yizhe Li , Peter I. Cowin , Bing Wang , Annette Kleppe , Tim Comyn , David Hall Journal Of The European Ceramic Society DOI: 10.1016/j.jeurceramsoc.2021.06.019 Diamond Proposal Number(s): [24144] Open Access Show Abstract ▼ Abstract: We report an in-situ synchrotron X-ray diffraction study of K0.5Bi0.5TiO3-BiFeO3-PbTiO3 ceramics, which exhibit a Tc of around 450 °C. The electromechanical actuation mechanisms comprise contributions from coexisting tetragonal and rhombohedral phases. The tetragonal {200} grain family exhibited the highest effective lattice strain, up to 8.2 ×10-3 at 5 kV/mm. Strong strain anisotropy in the tetragonal phase and field-induced intergranular stresses facilitate a partial transformation from tetragonal (high strain anisotropy) to rhombohedral (low strain anisotropy) at high electric field levels, with an average linear transformation strain of -1.54×10-3. The domain switching behavior was effectively enhanced in both tetragonal and rhombohedral phases after the phase transformation, due to the release of intergranular stress. This observed self-adapting mechanism in tuning intergranular stress through partial phase switching in the morphotropic KBT-BF-PT composition with large lattice distortion could also be exploited in other perovskite systems in order to achieve high performance high temperature piezoelectric ceramics.	Jun 2021
I15-Extreme Conditions	Internal resistive heating of non-metallic samples to 3000 K and >60 GPa in the diamond anvil cell Benedict J. Heinen , James W. E. Drewitt , Michael J. Walter , Charles Clapham , Fei Qin , Annette K. Kleppe , Oliver T. Lord Review Of Scientific Instruments 92 DOI: 10.1063/5.0038917 Diamond Proposal Number(s): [21972] Open Access Show Abstract ▼ Abstract: High pressure–temperature experiments provide information on the phase diagrams and physical characteristics of matter at extreme conditions and offer a synthesis pathway for novel materials with useful properties. Experiments recreating the conditions of planetary interiors provide important constraints on the physical properties of constituent phases and are key to developing models of planetary processes and interpreting geophysical observations. The laser-heated diamond anvil cell (DAC) is currently the only technique capable of routinely accessing the Earth’s lower-mantle geotherm for experiments on non-metallic samples, but large temperature uncertainties and poor temperature stability limit the accuracy of measured data and prohibits analyses requiring long acquisition times. We have developed a novel internal resistive heating (IRH) technique for the DAC and demonstrate stable heating of non-metallic samples up to 3000 K and 64 GPa, as confirmed by in situ synchrotron x-ray diffraction and simultaneous spectroradiometric temperature measurement. The temperature generated in our IRH-DAC can be precisely controlled and is extremely stable, with less than 20 K variation over several hours without any user intervention, resulting in temperature uncertainties an order of magnitude smaller than those in typical laser-heating experiments. Our IRH-DAC design, with its simple geometry, provides a new and highly accessible tool for investigating materials at extreme conditions. It is well suited for the rapid collection of high-resolution P–V–T data, precise demarcation of phase boundaries, and experiments requiring long acquisition times at high temperature. Our IRH technique is ideally placed to exploit the move toward coherent nano-focused x-ray beams at next-generation synchrotron sources.	Jun 2021
NONE-No attached Diamond beamline	Kernowite, Cu2Fe(AsO4)(OH)4⋅4H2O, the Fe 3+ -analogue of liroconite from Cornwall, UK M. S. Rumsey , M. D. Welch , J. Spratt , A. K. Kleppe , M. Števko Mineralogical Magazine DOI: 10.1180/mgm.2021.40 Show Abstract ▼ Abstract: The occurrence, chemical composition and structural characterization of the new mineral 3+ kernowite, ideally Cu2Fe(AsO4)(OH)4·4H2O, the Fe3+ -analogue of lirconite Cu2Al(AsO4)(OH)4·4H2O, are described. Kernowite occurs on specimens likely sourced from the Wheal Gorland mine, St Day, Cornwall, U.K in the cavities of a quartz-gossan rich in undifferentiated micro-crystalline grey sulphides and poorly crystalline arsenic phases including both pharmacosiderite and olivenite group minerals. The average composition of kernowite determined from several holotype fragments by electron microprobe analysis is Cu1.88(Fe0.79Al0.09)Σ0.88(As1.12O4)(OH)4·3.65H2O. The structure of kernowite has been determined in monoclinic space group I2/a (a non-standard setting of C2/c) by single-crystal X-ray diffraction to R1 = 0.025, wR2 = 0.051, Goodness-of-fit = 1.112. Unit-cell parameters from SCXRD are a = 12.9243(4)Å, b = 7.5401(3)Å, c = 10.0271(3)Å, Beta = 91.267(3), V = 976.91(6)Å3 (Z = 4). The chemical formula of this crystal indicated by SCXRD from refined site-scattering is Cu2(Fe3+0.84(1)Al0.16)AsO4(OH)4·4H2O. The network of hydrogen-bonding has been determined and is similar to that reported for liroconite from Wheal Gorland by Plumhoff et al. (2020).	May 2021
I15-Extreme Conditions	In situ poling X-ray diffraction studies of lead-free BiFeO3-SrTiO3 ceramics Zhilun Lu , Ge Wang , Linhao Li , Yuhe Huang , Antonio Feteira , Weichao Bao , Annette K. Kleppe , Fangfang Xu , Dawei Wang , Ian M. Reaney Materials Today Physics 71 DOI: 10.1016/j.mtphys.2021.100426 Diamond Proposal Number(s): [21714] Open Access Show Abstract ▼ Abstract: The origin of the large electrostrain in BiFeO3-BaTiO3 (BF-BT) ceramics is controversial and has been attributed to either a field-induced transition to a long-range ferroelectric (FE) state or to multi-symmetry, polar nanoregions within a pseudocubic matrix whose vectors approximately align with the direction of the applied field. The (1-x)BiFeO3-xSrTiO3 (BF-xST) solid solution is structurally and microstructurally similar to BF-BT and provides a further case study to assess the origin of electrostrain. In BF-xST, electrostrain is optimised at x = 0.4 (0.15%) which zero field, room temperature full-pattern X-ray diffraction (XRD) Rietveld refinement and scanning/transmission electron microscopy suggest is composed of 15% rhombohedral (R) cores, surrounded by 85% pseudocubic (PC) shells. In-situ poling synchrotron XRD revealed that all peaks remained singlet and exhibited no change in full width half maximum up to 100 kV cm-1, confirming the absence of long-range FE order and the retention of short-range polar order, despite the large applied field. Strain anisotropy (calculated from individual peaks) of ε220 > ε111 > ε200 and the associated strain orientation distribution however, indicate the existence of local orthorhombic (O), rhombohedral (R) and tetragonal (T) symmetries. The data therefore imply the existence under poling of multi-symmetry polar nanoregions in BF-0.4ST rather than a long FE phase, supporting the model described by Wang and co-workers (2019) for BF-BT compositions.	May 2021
I15-Extreme Conditions	High-pressure neutron powder diffraction study of ε-CL-20: A gentler way to study energetic materials Sumit Konar , Steven Hunter , Carole A. Morrison , Paul L. Coster , Helen Maynard-Casely , Jonathan G. Richardson , William G. Marshall , Annette Kleppe , Stewart F. Parker , Colin R. Pulham The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.0c09967 Diamond Proposal Number(s): [4631, 6707] Show Abstract ▼ Abstract: High-pressure studies have been performed on the ε-form of the powerful explosive CL-20. Hydrostatic compression over the pressure range 0–12 GPa has been monitored using synchrotron X-ray powder diffraction. The potential effects of X-ray radiation damage were observed and circumvented through a follow-up compression study over the pressure range 0–7 GPa using neutron powder diffraction. This second study revealed smooth compression behavior, and the absence of any phase transitions. Intermolecular interaction energies as obtained using PIXEL calculations did not show any discontinuity upon the application of pressure. An isothermal equation of state has been determined, and the high-pressure response is supported by dispersion-corrected density functional theory calculations. Inelastic neutron scattering (experimental and simulated) spectra for the ε-form are in excellent agreement.	Dec 2020
I15-Extreme Conditions	Mechanism of enhanced energy storage in AgNbO3-based lead-free antiferroelectrics Zhilun Lu , Weichao Bao , Ge Wang , Shikuan Sun , Linhao Li , Jinglei Li , Huijing Yang , Hongfen Ji , Antonio Feteira , Dejun Li , Fangfang Xu , Annette K. Kleppe , Dawei Wang , Shi-Yu Liu , Ian M. Reaney Nano Energy DOI: 10.1016/j.nanoen.2020.105423 Diamond Proposal Number(s): [21714] Open Access Show Abstract ▼ Abstract: The mechanisms underpinning high energy storage in lead-free Ag1-3xNdxTayNb1-yO3 antiferroelectric (AFE) ceramics have been investigated. Rietveld refinements of in-situ synchrotron X-ray data reveal that the structure remains quadrupled and orthorhombic under electric field (E) but adopts a non-centrosymmetric space group, Pmc21, in which the cations exhibit a ferrielectric configuration. Nd and Ta doping both stabilise the AFE structure, thereby increasing the AFE-ferrielectric switching field from 150 to 350 kV cm-1. Domain size and correlation length of AFE/ferrielectric coupling reduce with Nd doping, leading to slimmer hysteresis loops. Pmax is optimised through A-site aliovalent doping which also decreases electrical conductivity, permitting the application of a larger E. These effects combine to enhance energy storage density to give Wrec = 6.5 J cm-3 for Ag0.97Nd0.01Ta0.20Nb0.80O3.	Sep 2020
I15-Extreme Conditions	Grguricite, CaCr2(CO3)2(OH)4.4H2O, a new alumohydrocalcite analogue M. S. Rumsey , M. D. Welch , J. Spratt , A. K. Kleppe Mineralogical Magazine DOI: 10.1180/mgm.2020.66 Show Abstract ▼ Abstract: The occurrence and characterization of a new member of the dundasite group are reported. Grguricite, ideally CaCr2(CO3)2(OH)4·4H2O, is the Cr-analogue of alumohydrocalcite, CaAl2(CO3)2(OH)4·4H2O and occurs as lilac crusts of very fine-grained crystalline aggregates in the Pb-Ba-V mineralization found at the Adeghoual Mine, Mibladen, Morocco (32°46′0′′ N, 4°37′59′′ W). The identification was based upon a close match with the X-ray powder diffraction data for alumohydrocalcite, the confirmation of anion components identified by Raman spectroscopy and the cation composition determined by electron-probe microanalysis. The empirical formula based upon 14 oxygen atoms per formula unit is Ca0.84Pb0.03Cr1.65Al0.39Mg0.02(CO3)2(OH)4·4H2O, with carbonate, hydroxyl and water contents set to those of the alumohydrocalcite stoichiometry. The fine-grained nature of the crystals (c. 0.5 x 0.1 x 5 μm) precluded a single-crystal X-ray study and both density and optical determinations. Grguricite is triclinic with space group P1 ̄. Unit-cell parameters refined from the powder diffraction data are: a = 5.724(2) Å, b = 6.5304(9) Å, c = 14.646(4) Å, α = 81.682(1)°, β = 83.712(2)°, γ = 86.365(2)°, V = 537.8(2) Å3, Z = 2. The five strongest peaks in the powder pattern are [dhkl , I/Imax, (hkl)]: [6.222, 100, (011)], [3.227, 87, (020)], [6.454, 63, (010)], [2.883, 58, (005, 023, 121)], [7.208, 45, (002)]. The mineral is named after Australian geologist Ben Grguric.	Sep 2020
I15-Extreme Conditions	Mechanical behavior and phase change of alkali-silica reaction products under hydrostatic compression Guoqing Geng , Zhenguo Shi , Andreas Leemann , Konstantin Glazyrin , Annette Kleppe , Dominik Daisenberger , Sergey Churakov , Barbara Lothenbach , Erich Wieland , Rainer Daehn Acta Crystallographica Section B Structural Science, Crystal Engineering And Materials 76, 674 - 682 DOI: 10.1107/S205252062000846X Diamond Proposal Number(s): [18643] Show Abstract ▼ Abstract: Alkali-silica reaction (ASR) causes severe degradation of concrete. The mechanical property of the ASR product is fundamental to the multiscale modeling of concrete behavior over the long term. Despite years of study, there is a lack of consensus regarding the structure and elastic modulus of the ASR product. Here, ASR products from both degraded field infrastructures and laboratory synthesis were investigated using high-pressure X-ray diffraction. The results unveiled the multiphase and metastable nature of ASR products from the field. The dominant phase undergoes permanent phase change via collapsing of the interlayer region and in-planar glide of the main layer, under pressure >2 GPa. The bulk moduli of the low- and high-pressure polymorphs are 27±3 and 46±3 GPa, respectively. The laboratory-synthesized sample and the minor phase in the field samples undergo no changes of phase during compression. Their bulk moduli are 35±2 and 76±4 GPa, respectively. The results provide the first atomistic-scale measurement of the mechanical property of crystalline ASR products.	Aug 2020
I15-Extreme Conditions	Structural ordering in liquid gallium under extreme conditions James W. E. Drewitt , Francesco Turci , Benedict J. Heinen , Simon G. Macleod , Fei Qin , Annette K. Kleppe , Oliver T. Lord Physical Review Letters 124 DOI: 10.1103/PhysRevLett.124.145501 Diamond Proposal Number(s): [18961] Open Access Show Abstract ▼ Abstract: The atomic-scale structure, melting curve, and equation of state of liquid gallium has been measured to high pressure ( p ) and high temperature ( T ) up to 26 GPa and 900 K by in situ synchrotron x-ray diffraction. Ab initio molecular dynamics simulations up to 33.4 GPa and 1000 K are in excellent agreement with the experimental measurements, providing detailed insight at the level of pair distribution functions. The results reveal an absence of dimeric bonding in the liquid state and a continuous increase in average coordination number ¯ n Ga Ga from 10.4(2) at 0.1 GPa approaching ∼ 12 by 25 GPa. Topological cluster analysis of the simulation trajectories finds increasing fractions of fivefold symmetric and crystalline motifs at high p − T . Although the liquid progressively resembles a hard-sphere structure towards the melting curve, the deviation from this simple description remains large ( ≥ 40 % ) across all p − T space, with specific motifs of different geometries strongly correlating with low local two-body excess entropy at high p − T .	Apr 2020
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

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