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61 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	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
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	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	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

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