Laurent Lebrun

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Papers by Laurent Lebrun

XRD, USAXS, SAXS and WAXS investigations of ferroelectric PZN-4.5PT nanoparticle thin films on APS sychrotron beamlines

Acta Crystallographica Section A Foundations and Advances, 2021

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Improvement of Electric Field Induced Compressive Electrostriction of Polyurethane Composites Film Homogeneously Dispersed with Carbon Nanoparticles

MATERIALS TRANSACTIONS, 2015

To obtain the high compressive electrostriction indicated by maximum strain (S max) at low electr... more To obtain the high compressive electrostriction indicated by maximum strain (S max) at low electric field (E max), a dependence of solidification thickness on S max was investigated for carbon nanoparticles dispersed polyurethane (PU) composite films. The thickness dependent S max at 20 MV/m from 7.52% for 143 µm thickness to 47.7% for 21 µm thickness exhibited linear relationship, which was parallel to that of pure PU. Both thinning and nanoparticles addition enhanced the S max within the linear relationship. Considering with crystalline volume fraction and crystalline periodicity, the thickness dependent S max was explained. Effects of nanoparticles addition on S max were probably contributed by the polarization enhancement induced by increasing the capacitance.

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Combination of electrostrictive polymers composites and electrets for energy harvesting capability

Polymers for Advanced Technologies, 2014

More recently, the development of electrostrictive polymers has generated novel opportunities for... more More recently, the development of electrostrictive polymers has generated novel opportunities for high-strain actuators. At present, the investigation of using electrostrictive polymers for energy harvesting is beginning to show potential for this application. Basically, the relative energy gain depends on the current induced by the mechanical strain and frequency. The aim of the present experimental work is to study the composites on the basis of terpolymer P(VDF-TrFE-CFE) filled with low concentrations of copper (Cu) powders. The scanning electron microscopy was performed essentially to verify the dispersion of the fillers within the polymeric matrix. The obtained results showed a relatively homogeneous dispersion for the microsized fillers and the existence of agglomerates for their nanosized counterparts. On the other hand, our experimental data show that the harvested power as well as the current is significantly important for nano-Cu fillers with respect to micro-Cu fillers by a factor of 45.9% in the case of the hybridization of electrostrictive polymers and electrets.

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Comparative characterization of rhombohedral and tetragonal PZN-PT single crystals

AIP Advances, 2011

Ferroelectric single crystals Pb(Zn 1/3 Nb 2/3)O 3-PbTiO 3 (PZN-PT) are promising full materials ... more Ferroelectric single crystals Pb(Zn 1/3 Nb 2/3)O 3-PbTiO 3 (PZN-PT) are promising full materials for nonresonant or large bandwidth transducers due to the large values of their piezoelectric properties (d ij , k ij) and their mechanical quality factor (Q ij). However the properties of these materials depend greatly on the content of titanium which influences very significantly the symmetry of the crystal. In this paper we try to understand the influence of the percentage of Titanium in these crystals by studying the two compositions that are in very different phases at room temperature (rhombohedral and tetragonal symmetries). Crystals of pure PZN-4.5PT and PZN-12PT were grown by a Flux technique. The typical single crystals obtained are brown yellow. The room temperature dielectric permittivity along the <001> direction is about 900 for the PZN-12PT, which is smaller than that of the PZN-4.5PT (5840). The Curie point T c of the tetragonal crystal is about 220 • C (which is higher than that of the rhombohedral one (166 • C)), while the ferroelectric phase transition temperature is 130 • C for the PZN-4.5PT single crystal. The remnant polarization and coercive field of <001> oriented crystals measured at 1 kHz are around 40 µC/cm 2 and 3.30 kV/cm, respectively for the PZN-4.5PT, 27µC/cm 2 and 11.1 kV/cm for the PZN-12PT single crystal. The d 33 versus uniaxial stress shows that this coefficient is more stable for the single crystal with low Ti than for that with high rate of Ti. The study of temperature stability on these crystals shows a possible presence of an unidentified phase in the low and negative range temperature for the PZN-4.5PT.

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Dielectric and Mechanical Nonlinear Behavior of Mn Doped PMN-35PT Ceramics

Journal of Modern Physics, 2010

This paper presents an investigation on dielectric and mechanical nonlinear properties in Mn-dope... more This paper presents an investigation on dielectric and mechanical nonlinear properties in Mn-doped PMN-35PT ceramics. The structural study of the ceramics verifies that the 1% mol Mn doped PMN-35PT is a pure perovskite phase with a tetragonal symmetry. SEM micrograph shows the same microstructural morphology of an undoped ceramic. From the EPR spectra, it has been concluded that the major part of Mn is present in Mn 2+ rather than in Mn 4+ form. The addition of Mn 2+ ions acts on the dielectric, piezoelectric and mechanical properties by decreasing the relative dielectric permittivity (3800 to 2074), the dielectric losses (0.60 to 0.53), the piezoelectric coefficient d 33 (650 to 403 pC/N), and increasing the mechanical quality factor Q m (78 to 317). It was found that in Mn 2+ doped ceramics the dielectric response can not be described by Rayleigh law. This result can be understood taking into account that reversible motion of the domain wall is a relevant contribution to response of this material.

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Non Linear Properties of Dense PIN-PT Ceramics

Materials Research Society Symposium Proceedings, 2008

Nonlinear measurements of dense 63PbIn 1/2 Nb 1/2-37PbTiO 3 (PIN-37PT) piezoceramics, was recorde... more Nonlinear measurements of dense 63PbIn 1/2 Nb 1/2-37PbTiO 3 (PIN-37PT) piezoceramics, was recorded at 1 kHz and at resonance under driven AC electric fields and axial static pressure. Influence of donor or softener (Mg, Nb) and acceptor or hardener (Mn) was investigated. Dependence of the real and imaginary parts of the dielectric constant on electric field was compared with PZT hard ceramics and PMN-PT soft ceramics. The mechanical nonlinear behavior of piezoelectric ceramics, characterized by two coefficients (α and β), was measured according to the CENELEC European Standards EN5034-3. The new mechanical nonlinear coefficient β measures the compliance variation. The α and β coefficients of PIN-37PT ceramics, 0.95×10 6 and 3.8×10 6 , are larger than that hard PZT8 (0.03×10 6 and 0.3×10 5).

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Influence of corona poling on the electrostrictive behavior of cellular polypropylene films

Sensors and Actuators A: Physical, 2012

ABSTRACT In this study, a quadratic electric field dependence of the strain on the −30 kV corona-... more ABSTRACT In this study, a quadratic electric field dependence of the strain on the −30 kV corona-charged cellular polypropylene (PP) was observed, which was found to mainly originate from electrostriction after evaluation of Maxwell stress effect. The −30 kV-charged sample presented a maximal strain twice as high as that of the non-charged sample for the same applied electric field. Both the dielectric constant and apparent electrostrictive coefficient of cellular PP were also seen to increase after corona poling treatment. We investigated such higher electrostrictive response from the behavior of surface potential decay, the TSC current and the thermal properties. From TSC current curves, it was found that a certain amount of charges became injected into the film. And then, the total charge within the PP was calculated by integrating the TSC current, which provided a convincing evidence for enhanced electrostriction of studied polymer. In addition, from DSC analysis, it was demonstrated that the corona treatment increased the crystallinity of the cellular PP, which was also highly desirable for enhancing the electrostrictive response. Increase in the permittivity and strain was explained experimentally and mathematically by using the space-charge theory and a simplified model.

Optimization of energy harvesting conversion using the hybridization of electrostrictive polymers and electrets

Sensors and Actuators A: Physical, 2013

ABSTRACT Energy harvesting is a means of clustering energy that is naturally present in the envir... more ABSTRACT Energy harvesting is a means of clustering energy that is naturally present in the environment by recovering it and then converting it into electricity for use in low-power electronics. After a brief introduction to energy harvesting using electrostrictive polymers and electrets, the second part of this article is focused on modelling. This section is divided into two: one part dealing with the electrostatic separate modelling based on physical domains using the FEM approach, to demonstrate that the electric field of the electret is applied also to the electrostrictive polymer and a second part dealing with modelling of the mechanical to electrical transduction in a case with an electrostrictive polymer working in pseudo-piezoelectric mode. The theoretical approach was then validated through various experiments and it was found that the output power density on the resistive load could reach a value that was six times higher than the classical approach. Highlights ► Hybridization of electrostrictive polymer and electrect for energy harvesting. ► Modelling that is able to predict the energy harvesting capabilities. ► Modelling the distribution of the electric field in the structure. Keywords Electroactive polymer; Energy harvesting; Electrostrictive polymer; Electret; FEM

Characterization of an electroactive polymer simultaneously driven by an electrical field and a mechanical excitation: An easy means of measuring the dielectric constant, the Young modulus and the electrostrictive coefficients

Physics Letters A, 2011

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Solidification Thickness Dependent Electrostriction of Polyurethane Films

MATERIALS TRANSACTIONS, 2012

To obtain large electrostriction (S max) at low electric filed (E max), a dependence of the solid... more To obtain large electrostriction (S max) at low electric filed (E max), a dependence of the solidification thickness (L) on S max was investigated for polyurethane films. Thinning the films remarkably enhanced S max at high E max at 20 MV/m, whereas thick films apparently exhibited higher S max at low E max of less than 3 MV/m. The L dependent S max from 5.01% for 140 µm thickness to 30.99% for 28 µm thickness exhibited linear relationship of pure polyurethane. Considering crystalline volume fraction and crystalline periodicity, the L dependent S max was explained.

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Segregation study and segregation modeling of Ti in Pb[(Mg1/3Nb2/3)0.60Ti0.40]O3 single crystal grown by Bridgman method

Materials Research Bulletin, 2006

Relaxor ferroelectric 0.60Pb(MgââNbââ)Oâ-0.40PbTiOâ single crystal was synthesized by Bridgman m... more Relaxor ferroelectric 0.60Pb(MgââNbââ)Oâ-0.40PbTiOâ single crystal was synthesized by Bridgman method. The segregation along the length of this crystal was observed by various physico-chemical characterization techniques. First, we note the evolution of the crystalline structure along the length of the as-grown crystals. The tetragonality factor c/a increases from 1.013 to 1.020. This evolution has been correlated with the Ti content determination by flame atomic absorption spectrometry, and it is shown that this is due to the evolution of Ti concentration along the crucible. Furthermore, a continuous increase of the fraction of tetragonal phase with increasing Ti content was observed. Hence, we could compare the experimental data with a standard segregation model and therefore calculate the effective segregation coefficient k {sub eff} for this composition. This coefficient was found to be equal to 0.849. The variation of the titanium content along the ingot causes an inevitable fluctuation of the dielectric and piezoelectric properties of the single crystal. Due to the increase of Ti concentration, the Curie point was 186 deg. C at the bottom of the ingot and 222 deg. C at the top. The piezoelectric coefficient of oriented and poled &lt;0 0 1&gt; samples varies from 1500 to 250 pC/N.

Electrocaloric properties of high dielectric constant ferroelectric ceramics

Journal of the European Ceramic Society, 2007

In the last two decades, the electrocaloric (EC) effect which is associated to the temperature (θ... more In the last two decades, the electrocaloric (EC) effect which is associated to the temperature (θ) dependence of the macroscopic polarization P(E, θ) under electric field E has been spasmodically studied in ferroelectric materials in order to find an alternative to the classical refrigeratory devices using freon. Basically, large electrocaloric temperature variation T originates from electric field-induced phase transition at the Curie temperature, but temperature changes of the sample are difficult to measure and depend on the experimental conditions. In this paper, the electrocaloric effect has been quantified directly and precisely by measuring the thermal energy exchanged under isothermal conditions using a modified Differential Scanning Calorimetry (DSC) apparatus. The DSC technique allowed to compare the EC properties of high-dielectric-constant (ε) ceramics in the vicinity of ferroelectric-paraelectric phase transition. The measurements were also simulated starting from polarization versus electric field hysteresis loops for different temperatures. It is shown excellent agreement between simulations and direct DSC measurements, except in a limited temperature range where the hysteresis of the polarization versus temperature is high.

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Electrostrictive polymers for mechanical energy harvesting

Journal of Polymer Science Part B: Polymer Physics, 2012

This article reviews the developments in electrostrictive polymers for energy harvesting. Electro... more This article reviews the developments in electrostrictive polymers for energy harvesting. Electrostrictive polymers are a variety of electroactive polymers that deform due to the electrostatic and polarization interaction between two electrodes with opposite electric charge. Electrostrictive polymers have been the subject of much interest and research over the past decade. In earlier years, much of the focus was placed on actuator configurations, and in more recent years, the focus has turned to investigating material properties that may enhance electromechanical activities. Since the last 5 years and with the development of low-power electronics, the possibility of using these materials for energy harvesting has been investigated. This review outlines the operating principle in energy scavenging mode and conversion mechanisms behind this generator technology, highlights some of its advantages over existing actuator technologies, identifies some of the challenges associated with its development, and examines the main focus of research within this field, including some of the potential applications. V

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Dielectric and mechanical nonlinearities of lang001rang oriented pure and doped single crystals of PZN-4.5PT

Journal of Physics D: Applied Physics, 2005

This paper presents an overview of nonlinear dielectric, electromechanical, piezoelectric relatio... more This paper presents an overview of nonlinear dielectric, electromechanical, piezoelectric relationships in pure and Mn doped single crystals PZN-4.5PT and some modelling. The study of Mn doping on lang001rang oriented PZN-4.5PT single crystals confirms that pure crystals have soft material behaviour, while doped ones have hard material behaviour. This change in structure of the material has an effect on the

Oxygen vacancies effect on ionic conductivity and relaxation phenomenon in undoped and Mn doped PZN-4.5PT single crystals

Journal of Physics D: Applied Physics, 2007

AC-impedance spectroscopic studies in the temperature range 550-700 • C are carried out on undope... more AC-impedance spectroscopic studies in the temperature range 550-700 • C are carried out on undoped and Mn doped PZN-PT single crystals grown by the flux method. The variation of dielectric permittivity with temperature at different frequencies shows normal ferroelectric and relaxor-like dependence for the doped and undoped crystals, respectively. Temperature-dependent spectroscopic modulus plots reveal a much broader peak for PZN-4.5PT + 1%Mn compared with that for PZN-4.5PT, which is different from the dielectric behaviour of the doped one. Complex modulus imaginary part (Z) versus real part (Z) plots fit well with one semicircle thus indicating only bulk contribution. The relaxation observed in the spectroscopic plots was assigned to mobile relaxor species such as oxygen vacancies and ions. No such relaxation could be observed for PZN-4.5PT + 1%Mn in the dielectric measurements. For both undoped and Mn doped crystals, the conduction behaviour was modelled by the universal dynamic response equation and by the NTC (negative temperature coefficient) materials resistance-temperature behaviour. A large difference in behaviour was found between the two single crystals such as the thermistor coefficients and the activation energy values, which could explain the increase in the thermal stability observed in the Mn doped PZN-PT single crystals by many studies.

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Electromechanical properties versus polarization and vibration directions of Pb((Zn1/3Nb2/3)0.955Ti0.045)O3single crystals grown by the modified Bridgman method

Journal of Physics D: Applied Physics, 2007

Relaxor-based piezoelectric 0.955Pb(Zn1/3Nb2/3)O3-0.045PbTiO3 (PZN-4.5PT) single crystals were gr... more Relaxor-based piezoelectric 0.955Pb(Zn1/3Nb2/3)O3-0.045PbTiO3 (PZN-4.5PT) single crystals were grown using the modified Bridgman method. The set of piezoelectric coefficients in the lateral mode has been measured. Samples with size of 10 × 2 × 1 mm3 were poled in the lang0 0 1rang and lang1 1 0rang crystallographic directions, with different vibration directions. Single crystals properties varied with the cut type.

Characteristics of Pb[(Zn1/3Nb2/3)0.955Ti0.045]O3 single crystals versus growth method

Journal of Crystal Growth, 2004

Relaxor-based piezoelectric 0.955Pb(Zn 1/3 Nb 2/3)O 3-0.045PbTiO 3 (PZN-4.5PT) single crystals we... more Relaxor-based piezoelectric 0.955Pb(Zn 1/3 Nb 2/3)O 3-0.045PbTiO 3 (PZN-4.5PT) single crystals were grown by two methods: the flux method and the modified Bridgman method from a flux of Pb 3 O 4 in sealed platinum crucibles at about 1200 C with a cooling rate of 0.8-1 C/h for flux method and a translation rate of 0.4-0.6 mm/h for MB method. A dedicated oven suitable for two methods has been specially built. The ratio PZN-PT/Flux was 40/60 mol % for the two methods. In this paper, some characteristics of the crystals obtained by flux and modified Bridgmann method such as the lattice parameters and the melting point are compared. The dielectric properties of the grown PZN-4.5PT crystals have been measured as a function of temperature at various frequencies. The phase transition from the tetragonal P4 mm to cubic phase takes place at 166 C for the crystals grown by Bridgmann modified method and Flux method.

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Single crystals and nonlinear process for outstanding vibration-powered electrical generators

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2006

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A comparison between several approaches of piezoelectric energy harvesting

Journal de Physique IV (Proceedings), 2005

This paper compares the performances of vibration-powered electrical generators using a piezoelec... more This paper compares the performances of vibration-powered electrical generators using a piezoelectric ceramic and a piezoelectric single crystal associated to several power conditioning interfaces. A new approach of the piezoelectric power conversion based on a non linear voltage processing is presented, leading to three novel high-performance techniques. Theoretical predictions and experimental results show that the novel techniques may increase the power harvested above 800% compared to standard techniques.

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Les matériaux piezoélectriques actuels : céramiques - monocristaux - composites

Annales de Chimie Science des Matériaux, 2004

Cet article dresse un etat de l'art sur les recherches concernant les materiaux piezoelectriq... more Cet article dresse un etat de l'art sur les recherches concernant les materiaux piezoelectriques actuels incluant les ceramiques PZT (PbZr x Ti (1-x) O 3 ), les monocristaux ferroelectriques a base de plomb et les composites. Dans le cas des ceramiques, l'accent est mis sur la stabilisation des caracteristiques avec des materiaux multisubstitues dopes avec du fluor. Les performances electromecaniques et electro-optiques des recents monocristaux sont ensuite examinees. Enfin la technologie des materiaux piezoelectriques composites est introduite, en particulier les recents developpements concernant les composites a fibres piezoelectriques.

Laurent Lebrun

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