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Dive into the research topics where Hugh Simons is active.

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Featured researches published by Hugh Simons.


Applied Physics Letters | 2011

Electric-field-induced strain mechanisms in lead-free 94%(Bi1/2Na1/2)TiO3–6%BaTiO3

Hugh Simons; John E. Daniels; Wook Jo; Robert Dittmer; Andrew J. Studer; Maxim Avdeev; Jürgen Rödel; Mark Hoffman

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.


Nature Communications | 2015

Dark-field X-ray microscopy for multiscale structural characterization

Hugh Simons; A. King; Wolfgang Ludwig; Carsten Detlefs; W. Pantleon; Søren Schmidt; I. Snigireva; A. Snigirev; Henning Friis Poulsen

Many physical and mechanical properties of crystalline materials depend strongly on their internal structure, which is typically organized into grains and domains on several length scales. Here we present dark-field X-ray microscopy; a non-destructive microscopy technique for the three-dimensional mapping of orientations and stresses on lengths scales from 100 nm to 1 mm within embedded sampling volumes. The technique, which allows ‘zooming’ in and out in both direct and angular space, is demonstrated by an annealing study of plastically deformed aluminium. Facilitating the direct study of the interactions between crystalline elements is a key step towards the formulation and validation of multiscale models that account for the entire heterogeneity of a material. Furthermore, dark-field X-ray microscopy is well suited to applied topics, where the structural evolution of internal nanoscale elements (for example, positioned at interfaces) is crucial to the performance and lifetime of macro-scale devices and components thereof.


Applied Physics Letters | 2013

Origin of large recoverable strain in 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 near the ferroelectric-relaxor transition

Hugh Simons; John E. Daniels; Julia Glaum; Andrew J. Studer; Jacob L. Jones; Mark Hoffman

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.


Journal of Applied Physics | 2012

Domain fragmentation during cyclic fatigue in 94%(Bi1/2Na1/2)TiO3-6%BaTiO3

Hugh Simons; Julia Glaum; John E. Daniels; Andrew J. Studer; Andreas Liess; Jürgen Rödel; Mark Hoffman

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.


Scientific Reports | 2016

Dual strain mechanisms in a lead-free morphotropic phase boundary ferroelectric

Julian Walker; Hugh Simons; D. O. Alikin; A. P. Turygin; Vladimir Ya. Shur; A. L. Kholkin; Hana Uršič; Andreja Benčan; Barbara Malic; V. Nagarajan; Tadej Rojac

Electromechanical properties such as d33 and strain are significantly enhanced at morphotropic phase boundaries (MPBs) between two or more different crystal structures. Many actuators, sensors and MEMS devices are therefore systems with MPBs, usually between polar phases in lead (Pb)-based ferroelectric ceramics. In the search for Pb-free alternatives, systems with MPBs between polar and non-polar phases have recently been theorized as having great promise. While such an MPB was identified in rare-earth (RE) modified bismuth ferrite (BFO) thin films, synthesis challenges have prevented its realization in ceramics. Overcoming these, we demonstrate a comparable electromechanical response to Pb-based materials at the polar-to-non-polar MPB in Sm modified BFO. This arises from ‘dual’ strain mechanisms: ferroelectric/ferroelastic switching and a previously unreported electric-field induced transition of an anti-polar intermediate phase. We show that intermediate phases play an important role in the macroscopic strain response, and may have potential to enhance electromechanical properties at polar-to-non-polar MPBs.


Journal of Materials Chemistry C | 2016

Temperature dependent piezoelectric response and strain–electric-field hysteresis of rare-earth modified bismuth ferrite ceramics

Julian Walker; Hana Uršič; Andreja Benčan; Barbara Malic; Hugh Simons; Ian M. Reaney; Giuseppe Viola; V. Nagarajan; Tadej Rojac

The rare-earth (RE)-modified bismuth ferrite (BiFeO3 or BFO) family of ferroelectrics have uncomplicated lead-free chemistries and simple perovskite structures. Due to the high Curie transition temperature of the parent BiFeO3 perovskite (∼830 °C), they are promising piezoelectric materials for use at elevated temperatures. However, the influence of the specific RE species on the electromechanical behavior at high temperatures and above the coercive electric-field is not widely reported. Here, structural analysis over multiple length scales using X-ray diffraction, transmission electron microscopy and piezoresponse force microscopy is coupled with a high electric-field cycling study and in situ converse d33 measurements up to 325 °C for three RE–BFO ceramic compositions, Bi0.86Sm0.14FeO3, Bi0.88Gd0.12FeO3 and Bi0.91Dy0.09FeO3. The ceramics exhibit different phase assemblages with varying amounts of polar rhombohedral R3c and intermediate antipolar orthorhombic Pbam phases as a function of the RE species. During electric-field cycling at electric-fields with amplitudes of 160 kV cm−1, peak-to-peak strains of 0.23–0.27% are reached for all three compositions. However, there are qualitative differences in the field-induced strain and electric current behavior as a function of electric-field cycling and the materials exhibit an electrical-history dependent behavior. Bi0.91Dy0.09FeO3 possesses an improved d33 stability as a function of temperature relative to the parent BFO perovskite and the highest depolarization temperature among the three RE–BFO compositions, with a stable d33 of ∼22 pC N−1 up to 325 °C.


Scientific Reports | 2016

Simultaneous resonant x-ray diffraction measurement of polarization inversion and lattice strain in polycrystalline ferroelectrics.

S. Gorfman; Hugh Simons; T. Iamsasri; S. Prasertpalichat; D. P. Cann; Hyeokmin Choe; Ullrich Pietsch; Y. Watier; Jacob L. Jones

Structure-property relationships in ferroelectrics extend over several length scales from the individual unit cell to the macroscopic device, and with dynamics spanning a broad temporal domain. Characterizing the multi-scale structural origin of electric field-induced polarization reversal and strain in ferroelectrics is an ongoing challenge that so far has obscured its fundamental behaviour. By utilizing small intensity differences between Friedel pairs due to resonant scattering, we demonstrate a time-resolved X-ray diffraction technique for directly and simultaneously measuring both lattice strain and, for the first time, polarization reversal during in-situ electrical perturbation. This technique is demonstrated for BaTiO3-BiZn0.5Ti0.5O3 (BT-BZT) polycrystalline ferroelectrics, a prototypical lead-free piezoelectric with an ambiguous switching mechanism. This combines the benefits of spectroscopic and diffraction-based measurements into a single and robust technique with time resolution down to the ns scale, opening a new door to in-situ structure-property characterization that probes the full extent of the ferroelectric behaviour.


Applied Physics Letters | 2015

Temperature dependent polarization reversal mechanism in 0.94(Bi1/2Na1/2)TiO3-0.06Ba(Zr0.02Ti0.98)O3 relaxor ceramics

Julia Glaum; Hugh Simons; Jessica M. Hudspeth; Matias Acosta; John E. Daniels

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 tem...


Journal of Applied Crystallography | 2017

X-ray diffraction microscopy based on refractive optics

Henning Friis Poulsen; Anders Clemen Jakobsen; Hugh Simons; Sonja Rosenlund Ahl; Phil K. Cook; Carsten Detlefs

A formalism is presented for dark-field X-ray microscopy using refractive optics. The new technique can produce three-dimensional maps of lattice orientation and axial strain within millimetre-sized sampling volumes and is particularly suited to in situ studies of materials at hard X-ray energies. An objective lens in the diffracted beam magnifies the image and acts as a very efficient filter in reciprocal space, enabling the imaging of individual domains of interest with a resolution of 100 nm. Analytical expressions for optical parameters such as numerical aperture, vignetting, and the resolution in both direct and reciprocal spaces are provided. It is shown that the resolution function in reciprocal space can be highly anisotropic and varies as a function of position in the field of view. Inserting a square aperture in front of the objective lens facilitates disjunct and space-filling sampling, which is key for three-dimensional reconstruction and analysis procedures based on the conservation of integrated intensity. A procedure for strain scanning is presented. Finally the formalism is validated experimentally at an X-ray energy of 17 keV.


Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena | 2015

Sacrificial structures for deep reactive ion etching of high-aspect ratio kinoform silicon x-ray lenses

Frederik Stöhr; Jonas Michael-Lindhard; Jörg Hübner; Flemming Jensen; Hugh Simons; Anders Clemen Jakobsen; Henning Friis Poulsen; Ole Hansen

This article describes the realization of complex high-aspect ratio silicon structures with feature dimensions from 100 μm to 100 nm by deep reactive ion etching using the Bosch process. As the exact shape of the sidewall profiles can be crucial for the proper functioning of a device, the authors investigated how sacrificial structures in the form of guarding walls and pillars may be utilized to facilitate accurate control of the etch profile. Unlike other sacrificial structuring approaches, no silicon-on-insulator substrates or multiple lithography steps are required. In addition, the safe removal of the sacrificial structures was accomplished by thermal oxidation and subsequent selective wet etching. The effects of the dimensions and relative placement of sacrificial walls and pillars on the etching result were determined through systematic experiments. The authors applied this process for exact sidewall control in the manufacture of x-ray lenses that are very sensitive to sidewall shape nonuniformities...

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Henning Friis Poulsen

Technical University of Denmark

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Carsten Detlefs

European Synchrotron Radiation Facility

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Anders Clemen Jakobsen

Technical University of Denmark

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Frederik Stöhr

Technical University of Denmark

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Flemming Jensen

Technical University of Denmark

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Ole Hansen

Technical University of Denmark

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Sonja Rosenlund Ahl

Technical University of Denmark

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Jonas Michael-Lindhard

Technical University of Denmark

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John E. Daniels

University of New South Wales

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Mark Hoffman

University of New South Wales

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