ORCID Profile
0000-0002-4383-8482
Current Organisation
UNSW Sydney
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Publisher: AIP Publishing
Date: 15-08-2012
DOI: 10.1063/1.4745900
Abstract: 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 sub ision.
Publisher: Wiley
Date: 24-09-2020
Abstract: Ever‐increasing demand on electronic devices with ultrahigh‐density non‐volatile data storage has attracted great interest in novel ferroelectric memories based on conductive ferroelectric domain walls. Embedded in an insulating material, ferroelectric domain walls have the capability of being (re)created, displaced, erased, and altered in their spatial configurations and electronic characteristics. However, the domain wall conductivities are in most cases not yet sufficiently high to ensure the current density required to drive read‐out circuits operating at high speeds. In this work, a giant domain wall current ( µA) of a single charged domain wall is obtained through conductive atomic force microscopy with a bias field of 4 V. This is achieved in self‐assembled BiFeO 3 nanocrystals grown by sol‐gel method on Nb‐doped SrTiO 3 substrates. Local configurations of domains and domain wall types are studied using vector piezoresponse force microscopy and high‐resolution transmission electronic microscopy. The enhancement of the wall current is shown to be due to the formation of conducting pathways of charged defects accumulated along domain walls and traversing the nanocrystals. The erse domain walls can be manipulated by electric field in a perpendicular architecture. The perpendicular array structure of BiFeO 3 nanocrystals should have great potentials for developing perpendicular nanoelectronic prototypes.
Publisher: Elsevier BV
Date: 02-2023
Publisher: Elsevier BV
Date: 2015
Publisher: IOP Publishing
Date: 12-2006
Publisher: Elsevier BV
Date: 08-2009
Publisher: IOP Publishing
Date: 12-2006
Publisher: International Union of Crystallography (IUCr)
Date: 12-05-2009
Publisher: International Union of Crystallography (IUCr)
Date: 20-05-2010
Publisher: Elsevier BV
Date: 10-2015
Publisher: Elsevier BV
Date: 02-2017
Publisher: IOP Publishing
Date: 02-05-2017
Publisher: Elsevier BV
Date: 04-2021
Publisher: Wiley
Date: 25-09-2009
Publisher: Wiley
Date: 05-04-2023
Abstract: Piezocatalysis offers a means to transduce mechanical energy into chemical potential, harnessing physical force to drive redox reactions. Working in the solid state, we show here that piezoelectric BaTiO 3 nanoparticles can transduce mechanical load into a flux of reactive radical species capable of initiating solid state free radical polymerization. Activation of a BaTiO 3 powder by ball milling, striking with a hammer, or repeated compressive loading generates highly reactive hydroxyl radicals (⋅OH), which readily initiate radical chain growth and crosslinking of solid acrylamide, acrylate, methacrylate and styrenic monomers. Control experiments indicate a critical role for chemisorbed water on the BaTiO 3 nanoparticle surface, which is oxidized to ⋅OH via mechanoredox catalysis. The force‐induced production of radicals by compressing dry piezoelectric materials represents a promising new route to harness mechanical energy for solid state radical synthesis.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 04-06-2021
Abstract: Spinodal decomposition is discovered to be an effective way to strengthen magnesium alloy.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2018
Publisher: AIP Publishing
Date: 27-04-2017
DOI: 10.1063/1.4982674
Abstract: In this study, the possibility of determining the orientation distribution function (ODF) and quantifying the domain textures of polycrystalline ferroelectrics based on single high-energy X-ray diffraction images using a Rietveld refinement method is assessed. A spherical harmonics texture model is incorporated in the approach to determine the ODFs for phase constituents in poled lead-free ferroelectric ceramics (1 − x)(Bi0.5Na0.5)TiO3 − xBaTiO3 with x = 0.0625 and 0.075 from both single high-energy synchrotron diffraction images and full rotation diffraction data collected with the s les rotated perpendicular to the poling axis. A quantitative comparison is made between the complete pole figures and pole density profiles obtained from the ODFs extracted from the different diffraction data. The results show that a good approximation to the domain textures of fiber-type in poled ceramics as determined from the full rotation data can be obtained from single diffraction images, with the dominant pole densities within a maximum difference of ∼0.15 multiples of a random distribution. It thus demonstrates that single high-energy X-ray diffraction images are suitable for the quantification of domain texture in ferroelectric ceramics. The analysis validates the applicability of high-energy synchrotron X-day diffraction to observe the texture evolution in situ in ferroelectric ceramics under fast or continuous loading conditions.
Publisher: Wiley
Date: 26-08-2015
DOI: 10.1111/JACE.13839
Publisher: AIP Publishing
Date: 29-08-2016
DOI: 10.1063/1.4962125
Abstract: The electro-mechanical coupling mechanisms in polycrystalline ferroelectric materials, including a soft PbZrxTi1−xO3 (PZT) and lead-free 0.9375(Bi1/2Na1/2)TiO3-0.0625BaTiO3 (BNT-6.25BT), have been studied using a surface sensitive low-energy (12.4 keV) and bulk sensitive high-energy (73 keV) synchrotron X-ray diffraction with in situ electric fields. The results show that for tetragonal PZT at a maximum electric field of 2.8 kV/mm, the electric-field-induced lattice strain (ε111) is 20% higher at the surface than in the bulk, and non-180° ferroelectric domain texture (as indicated by the intensity ratio I002/I200) is 16% higher at the surface. In the case of BNT-6.25BT, which is pseudo-cubic up to fields of 2 kV/mm, lattice strains, ε111 and ε200, are 15% and 20% higher at the surface, while in the mixed tetragonal and rhombohedral phases at 5 kV/mm, the domain texture indicated by the intensity ratio, I111/I111¯ and I002/I200, are 12% and 10% higher at the surface than in the bulk, respectively. The observed difference in the strain contributions between the surface and bulk is suggested to result from the fact that surface grains are not constrained in three dimensions, and consequently, domain reorientation and lattice expansion in surface grains are promoted. It is suggested that the magnitude of property difference between the surface and bulk is higher for the PZT than for BNT-6.25BT due to the level of anisotropy in the strain mechanism. The comparison of the results from different methods demonstrates that the intergranular constraints have a significant influence on the electric-field-induced electro-mechanical responses in polycrystalline ferroelectrics. These results have implications for the design of higher performance polycrystalline piezoelectrics.
Publisher: Elsevier BV
Date: 08-2009
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6RA22802J
Abstract: Conventionally, the stretching of rubber is modeled exclusively by rotations of segments of the embedded polymer chains i.e. changes in entropy.
Publisher: Springer Science and Business Media LLC
Date: 2012
Publisher: Wiley
Date: 20-01-2009
Abstract: The dissolution process of metal complexes in ionic liquids was investigated by a multiple-technique approach to reveal the solvate species of the metal in solution. The task-specific ionic liquid betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf(2)N]) is able to dissolve stoichiometric amounts of the oxides of the rare-earth elements. The crystal structures of the compounds [Eu(2)(bet)(8)(H(2)O)(4)][Tf(2)N](6), [Eu(2)(bet)(8)(H(2)O)(2)][Tf(2)N](6) x 2 H(2)O, and [Y(2)(bet)(6)(H(2)O)(4)][Tf(2)N](6) were found to consist of dimers. These rare-earth complexes are well soluble in the ionic liquids [Hbet][Tf(2)N] and [C(4)mim][Tf(2)N] (C(4)mim = 1-butyl-3-methylimidazolium). The speciation of the metal complexes after dissolution in these ionic liquids was investigated by luminescence spectroscopy, (1)H, (13)C, and (89)Y NMR spectroscopy, and by the synchrotron techniques EXAFS (extended X-ray absorption fine structure) and HEXS (high-energy X-ray scattering). The combination of these complementary analytical techniques reveals that the cationic dimers decompose into monomers after dissolution of the complexes in the ionic liquids. Deeper insight into the solution processes of metal compounds is desirable for applications of ionic liquids in the field of electrochemistry, catalysis, and materials chemistry.
Publisher: International Union of Crystallography (IUCr)
Date: 20-04-2016
DOI: 10.1107/S1600577516005075
Abstract: When studying electro-mechanical materials, observing the structural changes during the actuation process is necessary for gaining a complete picture of the structure–property relationship as certain mechanisms may be meta-stable during actuation. In situ diffraction methods offer a powerful and direct means of quantifying the structural contributions to the macroscopic strain of these materials. Here, a s le cell is demonstrated capable of measuring the structural variations of electro-mechanical materials under applied electric potentials up to 10 kV. The cell is designed for use with X-ray scattering techniques in reflection geometry, while simultaneously collecting macroscopic strain data using a linear displacement sensor. The results show that the macroscopic strain measured using the cell can be directly correlated with the microscopic response of the material obtained from diffraction data. The capabilities of the cell have been successfully demonstrated at the Powder Diffraction beamline of the Australian Synchrotron and the potential implementation of this cell with laboratory X-ray diffraction instrumentation is also discussed.
Publisher: AIP Publishing
Date: 07-12-2015
DOI: 10.1063/1.4937586
Abstract: The temperature at which the electric field induced long-range ordered ferroelectric state undergoes transition into the short-range ordered relaxor state, TF-R, is commonly defined by the onset of strong dispersion of the dielectric permittivity. However, this combined macroscopic property and structural investigation of the polarization reversal process in the prototypical lead-free relaxor 0.94(Bi1/2Na1/2)TiO3-0.06Ba(Zr0.02Ti0.98)O3 reveals that an applied electric field can trigger depolarization and onset of relaxor-like behavior well below TF-R. The polarization reversal process can as such be described as a combination of (1) ferroelectric domain switching and (2) a reversible phase transition between two polar ferroelectric states mediated by a non-polar relaxor state. Furthermore, the threshold fields of the second, mediated polarization reversal mechanism depend strongly on temperature. These results are concomitant with a continuous ferroelectric to relaxor transition occurring over a broad temperature range, during which mixed behavior is observed. The nature of polarization reversal can be illustrated in electric-field-temperature (E-T) diagrams showing the electric field litudes associated with different polarization reversal processes. Such diagrams are useful tools for identifying the best operational temperature regimes for a given composition in actuator applications.
Publisher: AIP Publishing
Date: 13-11-2017
DOI: 10.1063/1.5008271
Abstract: The phase boundaries within (Bi0.5Na0.5TiO3)x(BaTiO3)y(SrTiO3)1−x−y with x ≥ 0.68 have been outlined. This was achieved using a combinatorial s le fabrication method and scanning synchrotron X-ray diffraction to rapidly characterise crystallographic structures over a large region of phase space. A parametric refinement method was used to clearly outline the phase boundaries as a function of the composition. The pseudo-cubic structure from the high strain non-ergodic Bi0.5Na0.5TiO3-BaTiO3 composition extends into the phase diagram with doping of SrTiO3, with regions of tetragonal and rhombohedral in the BaTiO3 and Bi0.5Na0.5TiO3 ends, respectively. This information can be used in conjunction with further compositional modifications to develop high strain piezoceramics that make use of electric-field-induced phase transformations and further understand the mechanisms in ergodic vs non-ergodic relaxors.
Publisher: SAGE Publications
Date: 22-07-2011
Abstract: High-energy synchrotron X-ray diffraction offers the unique combination of high spatial resolution and bulk material penetration power, which is well suited for the investigation of strain fields around cracks in engineering materials. The speed of data acquisition also lends itself to the observation of in-situ processes, such as crack propagation. This potential has been only partially explored over the last decade, and this paper reviews some basic advances with a view to future developments.
Publisher: Elsevier BV
Date: 10-2018
Publisher: AIP Publishing
Date: 16-06-2016
DOI: 10.1063/1.4953641
Abstract: Microscopic origins of the electric-field-induced strain for three compositions of Bi1/2(Na1−xKx)1/2TiO3 (x = 0.14, 0.18, and 0.22) (BNKT100x) ceramics have been compared using in situ high-energy (87.12 keV) X-ray diffraction. In the as-processed state, average crystallographic structure of BNKT14 and BNKT18 were found to be of rhombohedral symmetry, while BNKT22 was tetragonal. Diffraction data collected under electric field showed that both the BNKT14 and BNKT18 exhibit induced lattice strain and non-180° ferroelectric domain switching without any apparent phase transformation. The BNKT22 composition, in addition to the lattice strain and domain switching, showed an electric-field-induced transformation from a tetragonal to mixed tetragonal-rhombohedral state. Despite the difference in the origin of microscopic strain responses in these compositions, the measured macroscopic poling strains of 0.46% (BNKT14), 0.43% (BNKT18), and 0.44% (BNKT22) are similar. In addition, the application of a second poling field of opposite polarity to the first increased the magnitude of non-180° ferroelectric domain texture. This was suggested to be related to the existence of an asymmetric internal bias field.
Publisher: AIP Publishing
Date: 27-03-2014
DOI: 10.1063/1.4869786
Abstract: The electric-field-induced strain response mechanism in a polycrystalline ceramic/ceramic composite of relaxor and ferroelectric materials has been studied using in situ high-energy x-ray diffraction. The addition of ferroelectric phase material in the relaxor matrix has produced a system where a small volume fraction behaves independently of the bulk under an applied electric field. Inter- and intra-grain models of the strain mechanism in the composite material consistent with the diffraction data have been proposed. The results show that such ceramic/ceramic composite microstructure has the potential for tailoring properties of future piezoelectric materials over a wider range than is possible in uniform compositions.
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 04-2010
Publisher: Elsevier BV
Date: 11-2022
Publisher: AIP Publishing
Date: 15-05-2007
DOI: 10.1063/1.2733636
Abstract: The polarization reversal mechanism in [111]c-oriented Pb(Zn1∕3Nb2∕3)O3−xPbTiO3 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° 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, τ, of approximately 5.7 s. These large time constants correlate with a frequency dependence of the macroscopic strain-field response.
Publisher: American Physical Society (APS)
Date: 19-08-2020
Publisher: Springer Science and Business Media LLC
Date: 10-2015
DOI: 10.1038/SREP14678
Abstract: The atomic-scale response of dielectrics/ferroelectrics to electric fields is central to their functionality. Here we introduce an in situ characterization method that reveals changes in the local atomic structure in polycrystalline materials under fields. The method employs atomic pair distribution functions (PDFs), determined from X-ray total scattering that depends on orientation relative to the applied field, to probe structural changes over length scales from sub-Ångstrom to several nanometres. The PDF is sensitive to local ionic displacements and their short-range order, a key uniqueness relative to other techniques. The method is applied to representative ferroelectrics, BaTiO 3 and Na ½ Bi ½ TiO 3 and dielectric SrTiO 3 . For Na ½ Bi ½ TiO 3 , the results reveal an abrupt field-induced monoclinic to rhombohedral phase transition, accompanied by ordering of the local Bi displacements and reorientation of the nanoscale ferroelectric domains. For BaTiO 3 and SrTiO 3 , the local/nanoscale structural changes observed in the PDFs are dominated by piezoelectric lattice strain and ionic polarizability, respectively.
Publisher: International Union of Crystallography (IUCr)
Date: 08-2019
DOI: 10.1107/S1600577519007902
Abstract: Parametric Rietveld refinement from powder diffraction data has been utilized in a variety of situations to understand structural phase transitions of materials in situ . However, when analysing data from lower-resolution two-dimensional detectors or from s les with overlapping Bragg peaks, such transitions become difficult to observe. In this study, a weighted parametric method is demonstrated whereby the scale factor is restrained via an inverse tan function, making the phase boundary composition a refinable parameter. This is demonstrated using compositionally graded s les within the lead-free piezoelectric (BiFeO 3 ) x (Bi 0.5 K 0.5 TiO 3 ) y (Bi 0.5 Na 0.5 TiO 3 ) 1 –x–y and (Bi 0.5 Na 0.5 TiO 3 ) x (BaTiO 3 ) 1– x systems. This has proven to be an effective method for diffraction experiments with relatively low resolution, weak peak splitting or compositionally complex multiphase s les.
Publisher: Elsevier BV
Date: 10-2018
Publisher: Elsevier BV
Date: 09-2201
Publisher: American Chemical Society (ACS)
Date: 21-07-2016
Abstract: Bismuth ferrite (BiFeO3) is difficult to pole because of the combination of its high coercive field and high electrical conductivity. This problem is particularly pronounced in thick films. The poling, however, must be performed to achieve a large macroscopic piezoelectric response. This study presents evidence of a prominent and reproducible self-poling effect in few-tens-of-micrometer-thick BiFeO3 films. Direct and converse piezoelectric measurements confirmed that the as-sintered BiFeO3 thick films yield d33 values of up to ∼20 pC/N. It was observed that a significant self-poling effect only appears in cases when the films are heated and cooled through the ferroelectric-paraelectric phase transition (Curie temperature TC ∼ 820 °C). These self-poled films exhibit a microstructure with randomly oriented columnar grains. The presence of a compressive strain gradient across the film thickness cooled from above the TC was experimentally confirmed and is suggested to be responsible for the self-poling effect. Finally, the macroscopic d33 response of the self-poled BiFeO3 film was characterized as a function of the driving-field frequency and litude.
Publisher: Wiley
Date: 12-09-2016
DOI: 10.1111/JACE.14481
Publisher: Springer Science and Business Media LLC
Date: 25-06-2018
DOI: 10.1038/S41563-018-0116-3
Abstract: The characteristic functionality of ferroelectric materials is due to the symmetry of their crystalline structure. As such, ferroelectrics lend themselves to design approaches that manipulate this structural symmetry by introducing extrinsic strain. Using in situ dark-field X-ray microscopy to map lattice distortions around deeply embedded domain walls and grain boundaries in BaTiO
Publisher: Wiley
Date: 15-05-2014
DOI: 10.1111/JACE.12982
Publisher: AIP Publishing
Date: 16-09-2013
DOI: 10.1063/1.4821446
Abstract: The structural origin of the mechanical double loop behavior of polycrystalline BaTiO3 at temperatures just above the Curie point has been investigated using in situ high-energy synchrotron x-ray diffraction during uniaxial compressive mechanical loading. The results show a stress-induced transition from the high temperature paraelastic cubic phase to a ferroelastic tetragonal phase with a domain texture close to the saturated state. The nature of the observed stress-induced phase transition was influenced by the proximity of the temperature to the Curie point. With increasing temperature above the Curie point, the transition stress increased while the rate of the transition decreased.
Publisher: Wiley
Date: 03-07-2012
Publisher: Wiley
Date: 05-04-2023
Abstract: Piezocatalysis offers a means to transduce mechanical energy into chemical potential, harnessing physical force to drive redox reactions. Working in the solid state, we show here that piezoelectric BaTiO 3 nanoparticles can transduce mechanical load into a flux of reactive radical species capable of initiating solid state free radical polymerization. Activation of a BaTiO 3 powder by ball milling, striking with a hammer, or repeated compressive loading generates highly reactive hydroxyl radicals (⋅OH), which readily initiate radical chain growth and crosslinking of solid acrylamide, acrylate, methacrylate and styrenic monomers. Control experiments indicate a critical role for chemisorbed water on the BaTiO 3 nanoparticle surface, which is oxidized to ⋅OH via mechanoredox catalysis. The force‐induced production of radicals by compressing dry piezoelectric materials represents a promising new route to harness mechanical energy for solid state radical synthesis.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 27-03-2020
Abstract: An ultrahigh electric field–induced strain of 0.9% (under 1 kV mm −1 ) is achieved in lead-free ferroelectric crystals.
Publisher: Wiley
Date: 05-01-2022
Abstract: Electrical switching of ferroelectric domains and subsequent domain wall motion promotes strong piezoelectric activity, however, light scatters at refractive index discontinuities such as those found at domain wall boundaries. Thus, simultaneously achieving large piezoelectric effect and high optical transmissivity is generally deemed infeasible. Here, it is demonstrated that the ferroelectric domains in perovskite Pb(In 1/2 Nb 1/2 )O 3 –Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO 3 domain‐engineered crystals can be manipulated by electrical field and mechanical stress to reversibly and repeatably, with small hysteresis, transform the opaque polydomain structure into a highly transparent monodomain state. This control of optical properties can be achieved at very low electric fields (less than 1.5 kV cm −1 ) and is accompanied by a large ( 000 pm V −1 ) piezoelectric coefficient that is superior to linear state‐of‐the‐art materials by a factor of three or more. The coexistence of tunable optical transmissivity and high piezoelectricity paves the way for a new class of photonic devices.
Publisher: International Union of Crystallography (IUCr)
Date: 22-05-2015
DOI: 10.1107/S1600576715007669
Abstract: A method for the extension of the three-dimensional X-ray diffraction technique to allow the extraction of domain volume fractions in polycrystalline ferroic materials is presented. This method gives access to quantitative domain volume fractions of hundreds of independent embedded grains within a bulk s le. Such information is critical to furthering our understanding of the grain-scale interactions of ferroic domains and their influence on bulk properties. The method also provides a validation tool for mesoscopic ferroic domain modelling efforts. The mathematical formulations presented here are applied to tetragonal coarse-grained Ba 0.88 Ca 0.12 Zr 0.06 Ti 0.94 O 3 and rhombohedral fine-grained (0.82)Bi 0.5 Na 0.5 TiO 3 –(0.18)Bi 0.5 K 0.5 TiO 3 electroceramic materials. The fitted volume fraction information is used to calculate grain-scale non-180° ferroelectric domain switching strains. The absolute errors are found to be approximately 0.01 and 0.03% for the tetragonal and rhombohedral cases, which had maximum theoretical domain switching strains of 0.47 and 0.54%, respectively. Limitations and possible extensions of the technique are discussed.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0TC01300E
Abstract: We demonstrate a unique capability to control the formation and properties of skin layer structures in relaxor ferroelectrics by adjusting defect concentration. It is shown that the skin layer is polar and both electrically and optically active.
Publisher: Springer Science and Business Media LLC
Date: 02-10-2017
Publisher: Springer Science and Business Media LLC
Date: 09-02-2014
Publisher: Wiley
Date: 06-05-2019
Publisher: American Physical Society (APS)
Date: 20-04-2016
Publisher: AIP Publishing
Date: 11-02-2013
DOI: 10.1063/1.4790285
Abstract: Piezoceramics of composition 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 demonstrate large recoverable strain at elevated temperature (T & 75 °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 °C to 100 °C. Quantitative evaluation of the ferroelastic domain volume fraction in the field-induced phases enabled calculation of the strain contribution from non-180° 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.
Publisher: AIP Publishing
Date: 29-08-2016
DOI: 10.1063/1.4961533
Abstract: Phase-change actuator ceramics directly couple electrical and mechanical energies through an electric-field-induced phase transformation. These materials are promising for the replacement of the most common electro-mechanical ceramic, lead zirconate titanate, which has environmental concerns. Here, we show that by compositional modification, we reduce the grain-scale heterogeneity of the electro-mechanical response by 40%. In the materials investigated, this leads to an increase in the achievable electric-field-induced strain of the bulk ceramic of 45%. Compositions of (100–x)Bi0.5Na0.5TiO3–(x)BaTiO3, which initially possess a pseudo-cubic symmetry, can be tuned to undergo phase transformations to combined lower symmetry phases, thus decreasing the anisotropy of the transformation strain. Further, modelling of transformation strains of in idual grains shows that minimum grain-scale strain heterogeneity can be achieved by precise control of the lattice distortions and orientation distributions of the induced phases. The current results can be used to guide the design of next generation high-strain electro-mechanical ceramic actuator materials.
Publisher: Informa UK Limited
Date: 02-2014
Publisher: AIP Publishing
Date: 13-10-2008
DOI: 10.1063/1.2999623
Abstract: A combinatorial material synthesis and characterization technique is introduced and demonstrated wherein the ferroelectric behavior of a compositionally graded bulk ceramic is investigated during electrical loading. Using combined high-energy x-ray microdiffraction and fluorescence spectroscopy, non-180° domain wall motion of different compositions is measured and quantified as a function of composition across the gradation. The greatest amount of non-180° domain wall motion is found in s les containing the highest measured fraction of La dopant (2mol%).
Publisher: Elsevier BV
Date: 11-2006
Publisher: AIP Publishing
Date: 20-07-2009
DOI: 10.1063/1.3182679
Publisher: Elsevier BV
Date: 11-2006
Publisher: International Union of Crystallography (IUCr)
Date: 11-11-2008
DOI: 10.1107/S0021889808031488
Abstract: High-energy synchrotron X-ray diffraction using a monochromatic beam and large area detector offers a unique method for the study of directionally dependent s le information. The very short wavelengths and subsequent low scattering angles mean that scattering vectors at all angles approximately perpendicular to the beam direction are s led simultaneously. Here a method is proposed and demonstrated in which the magnitude and directions of structural and microstructural changes can be determined with higher resolution than was possible with previously used techniques. The method takes advantage of parametric refinements over multiple data sets using the profile fitting package TOPAS . Ex les of the technique applied to the study of strains in multiphase zirconium alloys and microstructural texture in ferroelastic/ferroelectric ceramics are given. The angular precision in lattice strain for a diffraction image with good statistics is found to be below 0.1°.
Publisher: Elsevier BV
Date: 11-2006
Publisher: Wiley
Date: 13-01-2022
DOI: 10.1111/JACE.18315
Abstract: Crystallographic texturing of ferroelectrics is known to improve the piezoelectrics response due to the alignment of optimal grain orientations in polycrystalline materials. Using high‐energy x‐ray diffraction, a ferroelastic self‐poling effect was observed in crystallographically textured 0.68 Pb(Mg 1/3 Nb 2/3 )O 3 − 0.32PbTiO 3 ceramic. It is shown that the BaTiO 3 platelet templates used to induce crystallographic texture imposed a biaxial strain causing ferroelastic domains to re‐orient parallel to the template plate normal. In‐situ high‐energy x‐ray diffraction was then used to characterize the response mechanisms of the material with applied electric fields. The textured ceramic produced a (111) lattice strain of 0.13% in the remanent state, and a 0.16% (111) unipolar lattice strain at 2 kV/mm while the untextured ceramic had a higher (111) lattice strain of 0.18% in the remanent state and a smaller (111) unipolar lattice strain at 2 kV/mm of 0.096%. This contrast in the strain magnitudes can be linked to the self‐poling effect. A strain mechanism incorporating the self‐poling effect is proposed, furthering our understanding of how crystallographic texture impacts the piezoelectric properties and providing a pathway for engineering the self‐poling effect to further enhance material response.
Publisher: Wiley
Date: 14-09-2018
DOI: 10.1111/JACE.16014
Publisher: Elsevier BV
Date: 03-2016
Publisher: Wiley
Date: 18-01-2011
Publisher: Informa UK Limited
Date: 11-02-2019
Publisher: Elsevier BV
Date: 02-2017
Publisher: AIP Publishing
Date: 13-08-2007
DOI: 10.1063/1.2771539
Publisher: Springer Science and Business Media LLC
Date: 19-10-2015
DOI: 10.1038/NMAT4435
Abstract: Ultra-lightweight alloys with high strength, ductility and corrosion resistance are desirable for applications in the automotive, aerospace, defence, biomedical, sporting and electronic goods sectors. Ductility and corrosion resistance are generally inversely correlated with strength, making it difficult to optimize all three simultaneously. Here we design an ultralow density (1.4 g cm(-3)) Mg-Li-based alloy that is strong, ductile, and more corrosion resistant than Mg-based alloys reported so far. The alloy is Li-rich and a solute nanostructure within a body-centred cubic matrix is achieved by a series of extrusion, heat-treatment and rolling processes. Corrosion resistance from the environment is believed to occur by a uniform lithium carbonate film in which surface coverage is much greater than in traditional hexagonal close-packed Mg-based alloys, explaining the superior corrosion resistance of the alloy.
Publisher: Elsevier BV
Date: 03-2016
Publisher: AIP Publishing
Date: 07-2010
DOI: 10.1063/1.3428373
Abstract: Polycrystalline 0.94(Bi1/2Na1/2)TiO3–0.06BaTiO3 s les were tested under uniaxial mechanical compression at various temperatures in the vicinity of the polar tetragonal to nonpolar tetragonal phase boundary. They are shown to display double loop-like stress-strain behavior, marked by a closed ferroelastic hysteresis loop. Thus, it forms a mechanical analog to the polarization-electric field hysteresis behavior of barium titanate above the Curie temperature. As temperature is increased there is an apparent loss of macroscopically observable ferroelasticity, despite the persistence of tetragonality. Macroscopic experimental results are discussed in conjunction with temperature-dependent and stress-dependent high-energy x-ray diffraction data. This reveals a phase transition below the Curie temperature, marked by a discontinuous change in lattice parameters and octahedral tilting during compressive mechanical loading.
Publisher: Elsevier BV
Date: 12-2019
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 08-2017
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2009
Publisher: Wiley
Date: 04-06-2011
Publisher: Elsevier BV
Date: 11-2016
Publisher: Springer Science and Business Media LLC
Date: 09-03-2016
DOI: 10.1038/SREP22820
Abstract: Understanding coupling of ferroic properties over grain boundaries and within clusters of grains in polycrystalline materials is hindered due to a lack of direct experimental methods to probe the behaviour of in idual grains in the bulk of a material. Here, a variant of three-dimensional X-ray diffraction (3D-XRD) is used to resolve the non-180° ferroelectric domain switching strain components of 191 grains from the bulk of a polycrystalline electro-ceramic that has undergone an electric-field-induced phase transformation. It is found that while the orientation of a given grain relative to the field direction has a significant influence on the phase and resultant domain texture, there are large deviations from the average behaviour at the grain scale. It is suggested that these deviations arise from local strain and electric field neighbourhoods being highly heterogeneous within the bulk polycrystal. Additionally, the minimisation of electrostatic potentials at the grain boundaries due to interacting ferroelectric domains must also be considered. It is found that the local grain-scale deviations average out over approximately 10–20 grains. These results provide unique insight into the grain-scale interactions of ferroic materials and will be of value for future efforts to comprehensively model these and related materials at that length-scale.
Publisher: Elsevier BV
Date: 12-2013
DOI: 10.1016/J.ACTBIO.2013.07.028
Abstract: The change in the biaxial residual stress state of hydroxyapatite crystals and collagen fibrillar structure in sections of bovine cortical bone has been investigated as a function of dehydration and radiation dose using combined small- and wide-angle X-ray scattering. It is shown that dehydration of the bone has a pronounced effect on the residual stress state of the crystalline phase, while the impact of radiation damage alone is less dramatic. In the initial hydrated state, a biaxial compressive stress of approximately -150 MPa along the bone axis exists in the hydroxyapatite crystals. As water evaporates from the bone material, the stress state moves to a tensile state of approximately 100 MPa. The collagen fibrillar structure is initially in a tensile residual stress state when the bone is hydrated and the state increases in magnitude slightly with dehydration. Radiation dose in continually hydrated s les also reduces the initial biaxial compressive stress magnitude in the hydroxyapatite phase however, the stress remains compressive. Radiation exposure alone does not appear to affect the stress state of the collagen fibrillar structure.
Publisher: AIP Publishing
Date: 13-05-2013
DOI: 10.1063/1.4805360
Abstract: The stability of electrically induced long-range ferroelectric order in a relaxor 0.94(Bi1/2Na1/2)TiO3-0.06BaTiO3 ceramic material has been investigated by temperature-dependent X-ray diffraction and electrical property measurements. The depolarization and ferroelectric-to-relaxor transition are identified as separate and discrete processes. It is observed that the induced ferroelectric domains first lose their ferroelectric/ferroelastic texture coincident with a peak signal in the thermally induced depolarization current. With further increase in temperature, the detextured ferroelectric domains are dissociated into nanoscale entities. This fragmentation marks the ferroelectric-to-relaxor transition. It is suggested that the ferroelectric-to-relaxor transition has features of a second order phase transition.
Publisher: Elsevier BV
Date: 06-2019
Publisher: AIP Publishing
Date: 20-06-2011
DOI: 10.1063/1.3602316
Abstract: Diffuse x-ray scattering intensities from a single crystal of 0.96(Bi1/2Na1/2TiO3)–0.04(BaTiO3) have been collected at room temperature with and without application of an electric field along the [100] direction. Distinct features in the diffuse scattering intensities indicate correlations on a nanometer length scale. It is shown that locally correlated planar-like structures and octahedral tilt-domains within the room temperature rhombohedral R3c phase are both electrically active and are irreversibly affected by application of an electric field of 4.3 kV/mm. The field dependence of these nanoscale structures is correlated with the relaxor behavior of the material by macroscopic permittivity measurements.
Publisher: AIP Publishing
Date: 16-03-2022
DOI: 10.1063/5.0080924
Abstract: The method of generating x-rays using the pyroelectric effect has garnered interest for applications that desire portability and low power consumption, particularly for real-time in-field and on-line analyses. However, the x-ray intensity produced by this type of x-ray generator is low and inconsistent compared to conventional x-ray tubes. The properties of several pyroelectric materials, including LiTaO3, LiNbO3, and PMN-xPT, were studied and subsequently tested on an in-house developed x-ray generator to explore their suitability for the application. The production of electrons to subsequently generate x-ray relies on the process of ferroelectric electron emission and field ionization to be dominant over charge compensation via the DC conductivity of the pyroelectric material. Given that the time of temperature change occurs faster than the material's charge relaxation time, it was found that the ratio of the pyroelectric coefficient to relative permittivity determined the performance of the x-ray generator. Thus, the x-ray count rates and end-point energies produced by LiTaO3 showed that it continues to be a strong candidate for such x-ray generation applications.
Publisher: AIP Publishing
Date: 12-2012
DOI: 10.1063/1.4768273
Abstract: The effect of a uniaxial compressive stress on the properties of BZT-BCT s les across the morphotropic phase boundary (MPB) is investigated using direct piezoelectric coefficient measurements. In contrast to many lead zirconate titanate compositions, the piezoelectric coefficient decreases monotonically with increasing stress and does not show an initial increase or plateau. Electrically softer rhombohedral and MPB compositions are found to be more susceptible to a decrease in piezoelectric coefficient under an increasing pre-stress than tetragonal compositions. Depoling due to ferroelastic domain switching alone, as observed by x-ray diffraction, does not explain this reduction, but instead a decreasing domain wall density is proposed to be responsible for reduced piezoelectric coefficients under increasing compressive stress. The relaxation of the piezoelectric response after complete unloading supports this proposed mechanism.
Publisher: Elsevier BV
Date: 06-1970
Publisher: American Association for the Advancement of Science (AAAS)
Date: 07-04-2023
Abstract: The piezoelectric properties of lead zirconate titanate [Pb(Zr,Ti)O 3 or PZT] ceramics could be enhanced by fabricating textured ceramics that would align the crystal grains along specific orientations. We present a seed-passivated texturing process to fabricate textured PZT ceramics by using newly developed Ba(Zr,Ti)O 3 microplatelet templates. This process not only ensures the template-induced grain growth in titanium-rich PZT layers but also facilitates desired composition through interlayer diffusion of zirconium and titanium. We successfully prepared textured PZT ceramics with outstanding properties, including Curie temperatures of 360°C, piezoelectric coefficients d 33 of 760 picocoulombs per newton and g 33 of 100 millivolt meters per newton, and electromechanical couplings k 33 of 0.85. This study addresses the challenge of fabricating textured rhombohedral PZT ceramics by suppressing the otherwise severe chemical reaction between PZT powder and titanate templates.
Publisher: Elsevier BV
Date: 07-2011
DOI: 10.1016/J.ACTBIO.2011.02.017
Abstract: Bone has a complex hierarchical structure. Combined wide angle X-ray diffraction and small angle X-ray scattering were used together with in situ tensile testing to investigate the deformation and failure mechanisms of bovine cortical bone at three material levels: (1) the atomic level, corresponding to the mineral crystal phase (2) the nano level, corresponding to the collagen fibrils (3) the macroscopic level. It was found that deformation was linear at all three levels up to a strain of 0.2% in the longitudinal tensile direction. At this critical strain a sudden 50% decrease in the fibrillar and mineral strains was observed. This suggests the presence of partial local damage that leads to inhomogeneous strain distributions within the probed gauge volume. This also gives rise to diffraction peak broadening in the mineral phase, as well as strain relaxation at the nanoscale. Above the critical strain the longitudinally oriented strains below the nanoscale remained constant at a reduced level until failure. This suggests that the lateral orientation of the nanostructures toughens the bone, while a higher material level dominated the subsequent deformation process, either by sliding between the lamellar layers or by the growth of microcracks. Analysis of the diffraction data also shows that the bone has compressive residual stress in the crystal phase. A better understanding of the basic mechanics of the hierarchical bone structure could be the basis to enhance research in biomimetics, developing new advanced materials, and to find solutions for orthopedic problems.
Publisher: Mineralogical Society of America
Date: 08-2010
DOI: 10.2138/AM.2010.3446
Publisher: Elsevier BV
Date: 06-2018
Publisher: AIP Publishing
Date: 21-02-2011
DOI: 10.1063/1.3557049
Abstract: 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 s le 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.
Publisher: Elsevier BV
Date: 07-2017
Publisher: AIP Publishing
Date: 14-12-2015
DOI: 10.1063/1.4937470
Abstract: The microscopic contributions to the electric-field-induced macroscopic strain in a morphotropic 0.93(Bi1/2Na1/2TiO3)−0.07(BaTiO3) with a mixed rhombohedral and tetragonal structure have been quantified using full pattern Rietveld refinement of in situ high-energy x-ray diffraction data. The analysis methodology allows a quantification of all strain mechanisms for each phase in a morphotropic composition and is applicable to use in a wide variety of piezoelectric compositions. It is shown that during the poling of this material 24%, 44%, and 32% of the total macroscopic strain is generated from lattice strain, domain switching, and phase transformation strains, respectively. The results also suggest that the tetragonal phase contributes the most to extrinsic domain switching strain, whereas the lattice strain primarily stems from the rhombohedral phase. The analysis also suggests that almost 32% of the total strain is lost or is a one-time effect due to the irreversible nature of the electric-field-induced phase transformation in the current composition. This information is relevant to on-going compositional development strategies to harness the electric-field-induced phase transformation strain of (Bi1/2Na1/2)TiO3-based lead-free piezoelectric materials for actuator applications.
Publisher: Springer Science and Business Media LLC
Date: 22-11-2018
DOI: 10.1038/S41467-018-07363-Y
Abstract: Dynamics of domain walls are among the main features that control strain mechanisms in ferroic materials. Here, we demonstrate that the domain-wall-controlled piezoelectric behaviour in multiferroic BiFeO 3 is distinct from that reported in classical ferroelectrics. In situ X-ray diffraction was used to separate the electric-field-induced lattice strain and strain due to displacements of non-180° domain walls in polycrystalline BiFeO 3 over a wide frequency range. These piezoelectric strain mechanisms have opposing trends as a function of frequency. The lattice strain increases with increasing frequency, showing negative piezoelectric phase angle (i.e., strain leads the electric field), an unusual feature so far demonstrated only in the total macroscopic piezoelectric response. Domain-wall motion exhibits the opposite behaviour, it decreases in magnitude with increasing frequency, showing more common positive piezoelectric phase angle (i.e., strain lags behind the electric field). Charge redistribution at conducting domain walls, oriented differently in different grain families, is demonstrated to be the cause.
Publisher: Elsevier BV
Date: 04-2017
Publisher: AIP Publishing
Date: 23-03-2020
DOI: 10.1063/5.0002235
Abstract: Domain-wall dynamics under strong, super-coercive electric fields in polycrystalline bismuth ferrite (BiFeO3) are not well established due to the experimental difficulties in processing high phase purity perovskite with low electrical conductivity. Overcoming these difficulties, here we present x-ray diffraction measurements carried out in situ during electrical poling with a trapezoidal electric-field to investigate the domain wall dynamics and lattice strain in this material. It is observed that during field r ing, microscopic strains, i.e., non-180° domain texture and lattice strain, increase simultaneously. During DC field dwell, however, a lattice strain decrease occurs over time, accompanied by an increase in the non-180° domain texture. This inverse time-dependent trend of microscopic strain mechanisms is speculated to be due to mobile charged defects residing in domain wall regions. The configuration of these charged point defects may also play a role in the observed post-poling relaxations of non-180° domain texture and macroscopic piezoelectric coefficients on removal of the field. Since conducting domain walls have been recently identified in a number of ferroelectrics, these results should significantly impact the understanding of strain mechanisms not only in BiFeO3 but on a broader range of ferroelectric materials.
Publisher: Informa UK Limited
Date: 09-2006
Publisher: Elsevier BV
Date: 09-2020
Publisher: Wiley
Date: 18-01-2021
DOI: 10.1111/JACE.17555
Publisher: Acoustical Society of America (ASA)
Date: 2023
DOI: 10.1121/10.0016754
Abstract: This work describes a 35.9 kHz ultrasonic transducer that incorporates a magnetic arrangement to apply a static-compressive prestress to a d32-mode relaxor ferroelectric single crystal drive-element. The magnetic arrangement produces a 22.5 N static-compressive force, inducing a static compression of ∼630 nm on the drive-element. Operating in air with a continuous-wave 10 V peak drive at ∼35.9 kHz, the measured resonant peak displacement of the transducers head-mass was 127 nm. This is well within the predicted static compression, thus, the drive-element is protected from damaging tensile stress. Under the same drive conditions and at an axial distance of 10 mm from the face of the head-mass, the measured acoustic pressure was ∼12 Pa. Analytical and finite element model predictions and the measured behaviour of a prototype device are presented and show good correlation, demonstrating that magnetic prestressing of the drive-element can be a viable alternative to the traditional bolt-cl .
Publisher: American Physical Society (APS)
Date: 04-04-2018
Publisher: AIP Publishing
Date: 02-05-2011
DOI: 10.1063/1.3582616
Abstract: High-energy synchrotron diffraction has been employed to demonstrate a time-dependent structural phase transition in 0.2K1/2Bi1/2TiO3–0.8Na1/2Bi1/2TiO3. It is demonstrated that the rapid increase in electric field (≥0.25 kV mm−1 s−1) induces a transformation from rhombohedral to mixed phase rhombohedral and tetragonal symmetry. When the electric field is applied slowly (& .25 kV mm−1 s−1), no transformation occurs, and rhombohedral symmetry is maintained. The extent of transformation increases with the rate of increase in electric field. High-speed capture of diffraction images (7 frames per second) has been used to show the evolution of the phase transformation as a function of time.
Publisher: Elsevier BV
Date: 2019
Publisher: AIP Publishing
Date: 05-2007
DOI: 10.1063/1.2720255
Abstract: 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° 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 +0.5Ec unipolar and ±0.5Ec bipolar, at 1 Hz, non-180° domain switching is found to contribute 34% and 40% of the macroscopically measured strain, respectively.
Publisher: AIP Publishing
Date: 02-11-2020
DOI: 10.1063/5.0018148
Abstract: A reduction in the orientation distribution of grains, via crystallographic texturing, is known to significantly enhance the electro-mechanical response in polycrystalline piezoelectrics. Through calculations of the electric-field-induced strain in phase-changing ceramics, the local strain heterogeneity was also found to increase with crystallographic texture. The increase in grain-scale strain heterogeneity potentially indicates greater stress concentrations within the polycrystal and may degrade the expected lifetime and fatigue behavior in these ceramics. In crystallographic symmetries with higher numbers of polarization directions, it was found that the magnitude of heterogeneity in the response was lower.
Publisher: Elsevier BV
Date: 03-2018
Publisher: Elsevier BV
Date: 08-2009
Publisher: Elsevier BV
Date: 12-2017
Publisher: Wiley
Date: 10-2009
Publisher: American Physical Society (APS)
Date: 26-05-2021
Publisher: Springer Science and Business Media LLC
Date: 04-04-2012
Publisher: Springer Science and Business Media LLC
Date: 08-2018
DOI: 10.1557/MRS.2018.156
Publisher: Elsevier BV
Date: 03-2014
Publisher: AIP Publishing
Date: 28-08-2006
DOI: 10.1063/1.2338756
Abstract: The dynamic piezoelectric response of ferroelectric ceramics is comprised of both intrinsic (piezoelectric lattice strain) and extrinsic (non-180° domain wall motion) components. Here the authors report direct measurements of non-180° domain wall motion in ceramic lead zirconate titanate during application of subcoercive cyclic driving electric fields using an in situ stroboscopic neutron diffraction technique. During unipolar cycling at 1Hz and half of the coercive field, non-180° domain switching gives rise to approximately 34% of the measured d33 coefficient of 400pm∕V.
Publisher: AIP Publishing
Date: 20-10-2014
DOI: 10.1063/1.4898573
Abstract: An electric-field-induced paraelectric cubic to ferroelectric tetragonal phase transformation has been directly observed in prototypical polycrystalline BaTiO3 at temperatures above the Curie point (TC) using in situ high-energy synchrotron X-ray diffraction. The transformation persisted to a maximum temperature of 4 °C above TC. The nature of the observed field-induced transformation and the resulting development of domain texture within the induced phase were dependent on the proximity to the transition temperature, corresponding well to previous macroscopic measurements. The transition electric field increased with increasing temperature above TC, while the magnitude of the resultant tetragonal domain texture at the maximum electric field (4 kV mm−1) decreased at higher temperatures. These results provide insights into the phase transformation behavior of a prototypical ferroelectric and have important implications for the development of future large-strain phase-change actuator materials.
No related grants have been discovered for John Daniels.