Browsing by Author "Daniels, JE"

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    Development of a new instrument to observe time-resolved neutron diffraction intensities in association with phase transitions
    (Australian Institute of Physics, 2005-01-31) Daniels, JE; Studer, AJ; Finlayson, TR; Hagen, ME
    The study of time-resolved diffraction intensities during a phase transition is important for gaining an understanding of the kinetics involved. Unfortunately the flux needed in order to achieve good counting statistics for a diffraction experiment during a single phase transition is very high. This problem is then compounded if the time scales which need to be observed are very small. Therefore techniques which can take advantage of the reversibility of some phase transitions are potentially beneficial in order to build up statistics. Stroboscopic techniques have been used in recent times to observe diffraction peak intensities with very good time resolution during the application of some type of perturbing field, driving a transition. Most commonly, and as will be the case with this instrument, high electric fields are used to switch single-crystal samples between their paraelectric and ferroelectric phases. Diffraction peaks are observed as a function of time during the switching period [1]. Other types of cycles which have also been used are stress [2], and temperature [3]. In order to carry out these types of experiments, a new capability has been added to The Australian Stress Scanner (TASS) instrument [4] at the High Flux Australian Reactor (HIFAR) operated by the Australian Nuclear Science and Technology Organisation (ANSTO). TASS is the former Triple Axis Spectrometer which, within the last couple of years, has been significantly refurbished (including the introduction of a multi-line, position-sensitive detector) to function as a two-axis diffractometer for strain mapping in engineering materials. This capability will allow for such stroboscopic experiments to be performed using the switching of high-voltage electric fields. The exact operation of the device is outlined in the experimental details section below. The common ferroelectric material, triglycine sulphate, will be used as a model crystal for the commissioning of the stroboscopic technique at HIFAR since, in a previous study involving stroboscopic diffraction intensity measurements at the ISIS [5], most unusual time dependencies for diffraction peak intensities from a TGS crystal in response to the switching of high-voltage electric fields applied to the crystal were observed.
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    Domain fragmentation during cyclic fatigue in 94%Bi(1/2)Na(1/2)TiO3-6%BaTiO3.
    (American Institute of Physics, 2012-01-01) Simons, H; Glaum, J; Daniels, JE; Studer, AJ; Liess, A; Rodel, J; Hoffman, M
    The fatigue of the lead-free piezoceramic 94%(Bi1/2Na1/2)TiO3-6%BaTiO3 was investigated under bipolar electric fields. Degradation of the polarization, strain, and permittivity was measured during the fatigue process, and correlated with structural data measured at incremental points in the fatigue process using neutron diffraction. The results suggest a two-stage fatigue mechanism whereby, following a field-induced phase transformation to a poled ferroelectric state, the domain structure becomes progressively fragmented by a repetitive process of domain wall pinning and subdivision. © 2012, American Institute of Physics.
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    Electric-field-induced phase transitions in co-doped Pb(Zr1−xTix)O3 at the morphotropic phase boundary
    (Taylor and Francis Online, 2014-02-28) Franzbach, DJ; Seo, YH; Studer, AJ; Zhang, Y; Glaum, J; Daniels, JE; Bencan, A; Malic, B; Webber, KG
    The strain- and polarization-electric field behavior was characterized at room temperature for Pb0.98Ba0.01(Zr1−xTix)0.98Nb0.02O3, 0.40  x  0.60. The investigated compositions were located in the vicinity of the morphotropic phase boundary, giving insight into the influence of crystal structure on the hysteretic ferroelectric behavior. The remanent strain of particular compositions is shown to be larger than theoretically allowed by ferroelectric switching alone, indicating the presence of additional remanent strain mechanisms. A phenomenological free energy analysis was used to simulate the effect of an applied electric field on the initial equilibrium phase. It is shown that electric-field-induced phase transitions in polycrystalline ferroelectrics can account for the experimental observations. The experimental and simulation results are contrasted to neutron diffraction measurements performed on representative compositions in the virgin and remanent states. © 2014, National Institute for Materials Science.
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    Electric-field-induced strain mechanisms in lead-free 94%(Bi1/2Na1/2)TiO3–6%BaTiO3.
    (American Institute of Physics, 2011-02-21) Simons, H; Daniels, JE; Jo, W; Dittmer, R; Studer, AJ; Avdeev, M; Rodel, J; Hoffman, M
    High resolution neutron diffraction has been used to investigate the structural origin of the large electric-field-induced remanent strain in 94(Bi1/2Na1/2)TiO3–6BaTiO3 ceramics. The virgin material was found to be a mixture of near-cubic phases with slight tetragonal and rhombohedral distortions of a0a0c+ and a−a−a− octahedral tilt type, respectively. Application of an electric field of 4.57 kV/mm transformed the sample to a predominantly rhombohedral a−a−a− modification with a significantly higher degree of structural distortion and a pronounced preferred orientation of the c-axis along the field direction. These electric field-induced structural effects contribute significantly to the macroscopic strain and polarization of this system. © 2011, American Institute of Physics
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    Ferroelastic contribution to the piezoelectric response in lead zirconate titanate by in situ stroboscopic neutron diffraction
    (Elsevier B. V., 2006-11-15) Jones, JL; Hoffman, M; Daniels, JE; Studer, AJ
    Ferroelastic domain switching during dynamic actuation is measured in situ for a piezoelectric lead zirconate titanate (PZT) ceramic utilizing a new capability developed on The Australian Strain Scanner (TASS) at ANSTO. Diffraction patterns are obtained as a function of time during a 1 Hz cycle. The change in the 0 0 2 and 2 0 0 diffraction intensities indicates there is ferroelastic domain switching at sub-coercive (weak) fields. © 2006 Elsevier B.V.
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    From single grains to texture
    (Wiley-VCH Verlag GmbH & Co. KGaA, 2009-10) Yan, K; Liss, KD; Garbe, U; Daniels, JE; Kirstein, O; Li, HJ; Dippenaar, RJ
    Structural materials, such as metals, ceramics, and their composites are most often polycrystalline. The nature, morphology, and composition of their microstructure determine in large measure the mechanical properties of the final product, and the art to design novel materials is to find particular arrangements which make them harder, more shock absorbing, heat resistant, or self-recovering upon damage and aging. The understanding of the basic processes and their interplay in a polycrystalline structure are most important for improved simulation of plastic deformation and to predict their thermo-mechanical behavior. © 2009, Wiley-VCH Verlag GmbH & Co. KGaA
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    A high-temperature-capacitor dielectric based on K0.5Na0.5NbO3-Modified Bi1/2Na1/2TiO3–Bi1/2K1/2TiO3
    (Wiley-Blackwell, 2012-11-01) Dittmer, R; Anton, EM; Jo, W; Simons, H; Daniels, JE; Hoffman, M; Pokorny, J; Reaney, IM; Rödel, J
    A high-temperature dielectric, (1–x)(0.6Bi1/2Na1/2TiO3–0.4Bi1/2K1/2TiO3)–xK0.5Na0.5NbO3, off the morphotropic phase boundary of the parent matrix 0.8Bi1/2Na1/2TiO3–0.2Bi1/2K1/2TiO3, has been developed for application as a high-temperature capacitor. In addition to temperature-dependent permittivity and dielectric loss, DC conductivity and field-dependent permittivity are reported. These properties are correlated with temperature-dependent structure data measured at different length scales using Raman spectroscopy and neutron diffraction. It is suggested that all materials investigated are ergodic relaxors with two types of polar nanoregions providing different relaxation mechanisms. The most attractive properties for application as high-temperature dielectrics are obtained in a material with x = 0.15 at less than 10% variation of relative permittivity of about 2100 between 54°C and 400°C. © 2012, Wiley-Blackwell.
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    Intrinsic and extrinsic contributions to the piezoelectric effect in soft lead zirconate titanate (PZT) ceramics by time-resolved neutron diffraction
    (The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Jones, JL; Daniels, JE; Studer, AJ; Hoffman, M; Finlayson, TR
    Piezoelectric ceramics are used in biomedical, naval, micromechanical, and many other precision engineering applications and therefore require a well-characterized, stable response. Utilizing a new capability developed on the The Australian Strain Scanner (TASS) at ANSTO, we have directly measured in situ the intrinsic and extrinsic t contributions to the piezoelectric effect in soft lead zirconate titanate (PZT) ceramics. The 002 and 200 diffraction peaks are measured as a function of time using a stroboscopic technique which enables timing resolutions of less than 30us. In other words, we have measured the 200 and 002 peak profiles as a function of time during piezoelectric activation. In this tetragonal crystal structure, a comparison of the 002 and 200 integrated intensity yields the non-180° domain switching contribution (extrinsic) while shifting of the peaks yields the change in 001 and 100 lattice strains (intrinsic). Both components lead to the macroscopic strain measured as the piezoelectric response, which is found to be a function of frequency and applied electric field. These results go toward explaining the nonlinearities of piezoelectric response versus frequency and magnitude of driving field measured in earlier work. © The Authors
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    Measurement and analysis of field-induced crystallographic texture using curved position-sensitive diffraction detectors
    (Springer Nature, 2014-02-09) Simons, H; Daniels, JE; Studer, AJ; Jones, JL; Hoffman, M
    This paper outlines measurement and analysis methodologies created for determining the structural responses of electroceramics to an electric field. A sample stage is developed to apply electric fields to ceramic materials at elevated temperatures during neutron diffraction experiments. The tested voltages and temperatures range from −20 kV to +20 kV and room temperature to 200 °C, respectively. The use of the sample environment for measuring the response of ferroelectric ceramics to an electrical stimulus is demonstrated on the instrument Wombat, a monochromatic neutron diffractometer employing a curved positive sensitive detector. Methodologies are proposed to account for the geometrical effects when vector fields are applied to textured materials with angularly dispersive detector geometries. Representative results are presented for the ferroelectric (Bi1/2Na1/2)TiO3-6%BaTiO3 (BNT-6BT) which show both phase transformation and ferroelectric domain texturing under the application of an electric field. This experimental and analysis approach is well suited for time-resolved measurements such as stroboscopic and in situ studies on a variety of electro-active materials.© 2014, Springer Science+Business Media New York.
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    Neutron diffraction studies of the ferroelectric/paraelectric transition in triglycine sulphate
    (Australian Institute of Physics, 2005-01-31) Daniels, JE; Piltz, RO; Hagen, ME; Finlayson, TR
    This research is a preliminary study in preparation for relaxation measurements using the stroboscopic neutron diffraction technique being presented at this congress. Triglycine sulphate, TGS, is a ferroelectric material with important potential for its pyroelectric applications. However, despite a number of structural studies of TGS in the literature, many have been done using x-ray diffraction and so uncertainty remains in regards to the precise hydrogen atom positions and the role of hydrogen bonding in the transition to the ferroelectric state. In this paper, structural studies using single-crystal neutron diffraction at temperatures in the vicinity of the Curie temperature, will be presented. © (2005) Australian Institute of Physics.
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    Neutron diffraction study of polycrystalline Ca1−xSrxTiO3 mixed perovskite materials
    (Elsevier B. V., 2006-11-15) Daniels, JE; Elcombe, MM; Finlayson, TR; Vance, ER
    Mixed perovskite samples, Ca1−xSrxTiO3, produced as solid ceramic materials, have been characterized using dynamic modulus and internal friction. These provide evidence for structural instabilities which have then been studied in detail using high-resolution neutron diffraction at particular temperatures using selected samples. Structural refinements indicate a low-temperature structural distortion to an orthorhombic Pbcm structure doubled along the c-axis. Details of the results and their analysis are presented and discussed in relation to other literature data for these mixed perovskite systems. © 2006 Elsevier B.V.
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    Neutron diffraction study of polycrystalline Ca1−xSrxTiO3 mixed perovskite materials
    (The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Daniels, JE; Elcombe, MM; Finlayson, TR; Vance, ER
    The mixed perovskite samples, Ca1−xSrxTiO3, produced as solid ceramic materials, have been characterized using dynamic modulus and internal friction. These provide evidence for structural instabilities which have then been studied in detail using high-resolution neutron diffraction at particular temperatures using selected samples. Structural refinements indicate a low-temperature structural distortion to an orthorhombic Pbcm structure doubled along the c-axis. Details of the results and their analysis are presented and discussed in relation to other literature data for these mixed perovskite systems. © The Authors
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    Neutron diffraction study of the polarization reversal mechanism in [111](c)-oriented Pb(Zn1/3Nb2/3)O-3-xPbTiO(3).
    (American Institute of Physics, 2007-05-24) Daniels, JE; Finlayson, TR; Davis, M; Damjanovic, D; Studer, AJ; Hoffman, M; Jones, JL
    The polarization reversal mechanism in [111](c)-oriented Pb(Zn1/3Nb2/3)O-3-xPbTiO(3) has been investigated by in-situ neutron diffraction. Stepwise static-field measurements of the (222)(c) rocking curves confirm a two-stage polarization reversal mechanism via a sequence of non-180 degrees domain reorientations. The time-resolved response has also been measured upon application of a bipolar square wave with a 30 s period to observe directly the relaxation times of diffracted neutron intensity during the reversal process. Upon application of a large antipolar field, the diffraction intensity increases quickly, before relaxing over a longer time period with an exponential decay constant, tau, of approximately 5.7 s. These large time constants correlate with a frequency dependence of the macroscopic strain-field response. © 2007, American Institute of Physics
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    Observations of temperature stability of γ-zirconium hydride by high-resolution neutron powder diffraction
    (Elsevier, 2016-03-15) Wang, ZY; Steuwer, A; Liu, N; Maimaitiyili, T; Avdeev, M; Blomqvist, J; Bjerkén, C; Curfs, C; Kimpton, JA; Daniels, JE
    The phase evolution in a zirconium–50 deuterium (Zr–50D, at.%) alloy system during thermal cycling has been investigated using in situ high-resolution neutron powder diffraction. The results showed that the peritectoid reaction α-Zr + δ-ZrD → γ-ZrD previously suggested to occur at high temperatures does not take place in the system. Slow cooling, from high temperatures (≥520 K) to room temperature at a rate of 5 K min−1, promoted the γ-hydride formation rather than fast cooling as reported earlier. In contrast to the observation that the δ-hydride present in the system remained at temperatures up to 740 K, the produced γ phase transformed to δ-hydride in the temperature range of 370 K–559 K, with the transformation completing at approximately 559 K. It is confirmed that the formation of the γ-hydride was reproducible with slow cooling, and a diffusion-controlled sluggish δ-to γ-hydride transformation is suggested to be responsible for the favorable development of γ-hydride during slow cooling. © 2015 Elsevier B.V.
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    Origin of large recoverable strain in 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 near the ferroelectric-relaxor transition
    (America Institute of Physics, 2013-02-11) Simons, H; Daniels, JE; Glaum, J; Studer, AJ; Jones, JL; Hoffman, M
    Piezoceramics of composition 0.94(Bi(0.5)Na(0.5))TiO(3)-0.06BaTiO(3) demonstrate large recoverable strain at elevated temperature (T > 75 degrees C), which is absent at room temperature. In situ neutron diffraction was used to measure changes in the crystallographic and domain structures during electric field application at temperatures ranging from 25 degrees C to 100 degrees C. Quantitative evaluation of the ferroelastic domain volume fraction in the field-induced phases enabled calculation of the strain contribution from non-180 degrees domain switching. The large recoverable strain is shown to be associated with the reversible nature of the phase transformation. These findings have implications to additional BNT-xBT-based composition and other relaxor ferroelectrics. © 2013, American Institute of Physics
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    Phase transformations in the Ca1-xSrxTiO3 perovskite system
    (Australian Institute of Physics, 2004-02-04) Daniels, JE; Elcombe, MM; Finlayson, TR; Vance, ER
    The mixed perovskite Ca1-xSrxTiO3 is one of the major constituent phases of SYNROC, a synthetic rock form proposed for the long term immobilisation of high-level nuclear waste [1]. A complete understanding of the crystal structures formed, and transitions within, each of the constituent phases is of vital importance to gaining a complete knowledge of the overall structural stability of SYNROC. This study investigated the transition temperatures and the space group symmetry of several samples between the composition values of x = 0.6 to 0.85. Previous studies of this compound have produced many conflicting results. It is believed that the reason for this is the sample preparation technique coupled with the form of the sample during experimentation, i.e., powder vs. polycrystalline solid. This study has attempted to produce samples using techniques closely related to those used in bulk SYNROC manufacture and to analyse these samples in their polycrystalline form as they would exist in SYNROC. Transition temperatures were determined by observing the dynamic Young’s modulus and internal friction of the samples between 4K and 420K using the Piezoelectric Ultrasonic Composite Oscillator Technique [2]. Classifications of the crystal structures formed were carried out using the High Resolution Powder Diffractometer at the Lucas Heights Research Reactor within the temperature range of 8K to 300K. Space group symmetries for each phase were then determined by Rietveld refinement.
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    Relationship between damage and hardness profiles in ion irradiated SS316 using nanoindentation–experiments and modelling
    (Elsevier, 2016-11) Saleh, M; Zaidi, Z; Hurt, C; Ionescu, M; Short, KT; Daniels, JE; Bhattacharyya, D; Munroe, P; Edwards, L
    In this work, the authors apply the “top-down” nanoindentation testing method to assess the mechanical property changes in ion-irradiated metallic alloys for three different ion energies in order to understand the relationship between ion energy, damage peak depth and hardness peak depth. The samples were irradiated with He+2 ions having 1, 2 and 3 MeV beam energies respectively. The curves for ΔH (radiation induced hardness) have been obtained by calculating the difference of the irradiated and unirradiated hardness curves after these were corrected for indentation size effect. Three-dimensional analytical and numerical models have been developed to obtain greater insight into the mechanisms involved in the nanoindentation processes, the nature of the plastic zone, and how these affect the hardness results, including the full hardness profiles with respect to depth. This is particularly valuable in situations where the damage profile is non-uniform, as in the present case, and provides the means to predict expected hardness peak positions and values for a given irradiation dose. Copyright © 2017 Elsevier B.V.
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    Residual stress measurements in vintage LPG pressure vessel welds, via neutron diffraction
    (Materials Research Forum LLC, 2016-07-03) Sozen, K; Paradowska, AM; Reid, M; Griffins, R; Daniels, JE
    Systems in power, petrochemical and refinery plants are subject to innumerable degradation mechanisms. Welds are the critical regions in such components. The focus of this project is on Liquid Petroleum Gas (LPG) storage vessels manufactured for Australian refineries in the 1960s. Residual stresses were measured in seam and circumferential welds extracted from the vessels. The aim of this project is to measure the residual stress storage vessel. This data will be used to engineer a procedure to repair the vintage steel plates of the pressure vessels with modern consumables and welding techniques. © The Authors
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    Time resolved neutron diffraction studies of triglycine sulphate near the ferroelectric transition during the application of high voltage electric fields
    (The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Daniels, JE; Finlayson, TR; Studer, AJ; Hagen, ME
    A new capability has been added to The Australian Stress Scanner (TASS), to allow the real-time response of neutron Bragg reflections to be monitored during the application of High Voltage fields. These experiments are performed using a stroboscopic technique which allows for timing resolutions below 30mus. Initial experiments using the new instrument have focussed on applying fields of up to 5kV/cm to samples of the ferroelectric triglycine sulphate (TGS), held at temperatures close to its ferroelectric/paraelectric transition temperature. The real-time responses of (0k0) type Bragg reflections in TGS show some unusual properties. In particular the (060) reflection shows several responses to the application of the field, including long relaxations over several seconds, as well as short spikes in intensity at field on and field off conditions which decay over approximately 150mus. This paper will present some of the recent data along with a discussion of the physical mechanisms leading to the intensity changes in Bragg reflections. © 2005 The Authors
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    Time-resolved diffraction measurements of electric-field-induced strain in tetragonal lead zirconate titanate
    (American Institute of Physics, 2007-05-01) Daniels, JE; Finlayson, TR; Studer, AJ; Hoffman, M; Jones, JL
    The dynamic electric-field-induced strain in piezoelectric ceramics enables their use in a broad range of sensor, actuator, and electronic devices. In piezoelectric ceramics which are also ferroelectric, this macroscopic strain is comprised of both intrinsic (piezoelectric) and extrinsic (non-180 degrees domain switching) strain components. Extrinsic contributions are accompanied by hysteresis, nonlinearity, and fatigue. Though technologically significant, direct measurement of these mechanisms and their relative contributions to the macroscopic response has not yet been achieved at driving frequencies of interest. Here we report measurements of these mechanisms in ceramic lead zirconate titanate during application of subcoercive cyclic driving electric fields using an in-situ stroboscopic neutron diffraction technique. Calculations are made from the diffraction measurements to determine the relative contributions of these different strain mechanisms. During applied electric field square waves of +0.5E(c) unipolar and +/- 0.5E(c) bipolar, at 1 Hz, non-180 degrees domain switching is found to contribute 34% and 40% of the macroscopically measured strain, respectively. © 2007, American Institute of Physics