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The flexoelectric effect is simply defined as the coupling between the strain gradient and polarization in solid dielectrics. It may be seen as an alternative transduction mechanism to the piezoelectric effect to directly sense the curvature of bent flexible thin structures. In the case of large curvatures, flexible and compliant sensors are required and soft polar elastomers may be suitable for curvature sensing. In this study, we report the flexoelectric characterization of soft semi-crystalline polyurethane (PU) films with thicknesses ranging from 1.7 μm to 350μm. Dynamic bending experiments have been performed on PU films deposited onto rigid steel substrates in the vicinity of the mechanical resonance frequency of the cantilever beams. Quasi-static flexoelectric coefficients of PU films could be obtained by using a classical oscillating model. A global large increase of μ'12 with the decreasing film thickness was found, especially for thicknesses lower than 25 μm. The variation of μ'12 is explained by the presence of a Young’s Modulus gradient through the thickness of PU films. Besides, a concomitant uncommon dramatic decrease in the dielectric constant is observed. The combination of these two effects contributes to enhancing the flexocoupling “F” constant with the decreasing thickness. At last, the potential use of a 6.6 μm-thick soft PU film as a large curvature sensor has been experimentally demonstrated by subjecting a flexible Aluminum foil/Polyethylene terephthalate bilayered cantilever to large deflections. A curvature of about 80m-1 (radius of curvature of ~1.2 cm) could be sensed under low frequency (3 Hz) bending motion. These results may pave the way for the development of low cost and easy to implement soft flexoelectric elastomer-based large curvature sensors on highly flexible metallic structures. [ABSTRACT FROM AUTHOR]

Highly flexible lead zirconate titanate, Pb(Zr,Ti)O3 (PZT), thin films have been realized by modified sol-gel process. The transverse piezoelectric coefficient d31 was determined from the tip displacement of bending-mode actuators made of PZT cantilever deposited onto bare or RuO2 coated aluminium substrate (16 µm thick). The influence of the thickness of ruthenium dioxide RuO2 and PZT layers was investigated for Pb(Zr0.57Ti0.43)O3. The modification of Zr/Ti ratio from 40/60 to 60/40 was done for 3 µm thick PZT thin films onto aluminium (Al) and Al/RuO2 substrates. A laser vibrometer was used to measure the beam displacement under controlled electric field. The experimental results were fitted in order to find the piezoelectric coefficient. Very large tip deflections of about 1 mm under low voltage (~8 V) were measured for every cantilevers at the resonance frequency (~180 Hz). For a given Zr/Ti ratio of 58/42, it was found that the addition of a 40 nm thick RuO2 interfacial layer between the aluminium substrate and the PZT layer induces a remarkable increase of the d31 coefficient by a factor of 2.7, thus corresponding to a maximal d31 value of 33 pC/N. These results make the recently developed PZT/Al thin films very attractive for both low frequency bending mode actuating applications and vibrating energy harvesting. [ABSTRACT FROM AUTHOR]

This study reports on the magnetoelectric coupling in a single piezoelectric ceramic disk subjected to both ac and dc magnetic fields perpendicularly applied to the sample's plane. Eddy currents are induced within the electrodes of the ceramic by ac magnetic flux via the Lenz-Faraday equation and yields Lorentz forces and stresses which are transferred to the piezoelectric ceramic. This latter transduces stress into electrical charges through electromechanical coupling in radial mode. The measured output magnetoelectric current could be successfully modeled using piezoelectric equations providing the inductively coupled voltage between the electrodes of the ceramic is taken into account. This voltage originates from the ac magnetic flux through the experimental loop, which is not a perfect short-circuit and yields two other contributions to the total current: piezoelectric current due to the induced electric field and the dielectric loop current. Radial velocity measurements confirmed the distinct contributions to the current. Thus, room temperature magnetic field detection is achievable using this single piezoelectric disk with a good sensitivity and linear response versus dc magnetic field change. [ABSTRACT FROM AUTHOR]

Presents information on a study which proposed a fluorine-oxygen substitution in lead zirconate titanate (PZT) ceramics. Application of PZT; Stress and temperature dependence of doped PZT ceramics; Results and discussion; Conclusions.

In this study, we report the magnetically induced electric field E in Pb(ZrTi)O (PZT) thin films, when they are subjected to both dynamic magnetic induction (magnitude B at 45 kHz) and static magnetic induction ( B) generated by a coil and a single permanent magnet, respectively. It is found that highest sensitivity to B- $$ {{\Delta \left| {E_{3} } \right|} \mathord{\left/ {\vphantom {{\Delta \left| {E_{3} } \right|} {\Delta B_{\text{dc}} }}} \right. \kern-0pt} {\Delta B_{\text{dc}} }} $$ -is achieved for the thin film with largest effective electrode. This magnetoelectric (ME) effect is interpreted in terms of coupling between eddy current-induced Lorentz forces (stress) in the electrodes of PZT and piezoelectricity. Such coupling was evidenced by convenient modelling of experimental variations of electric field magnitude with both B and B induction magnitudes, providing imperfect open circuit condition was considered. Phase angle of E versus B could also be modelled. At last, the results show that similar to multilayered piezoelectric-magnetostrictive composite film, a PZT thin film made with a simple manufacturing process can behave as a static or dynamic magnetic field sensor. In this latter case, a large ME voltage coefficient of $$ \alpha = {{\left| {E_{3} } \right|} \mathord{\left/ {\vphantom {{\left| {E_{3} } \right|} {B_{\text{ac}} }}} \right. \kern-0pt} {B_{\text{ac}} }} = 3.55\,{\text{V}}/{\text{cm}}\,{\text{Oe}} $$ under B = 0.3 T was found. All these results may provide promising low-cost magnetic energy harvesting applications with microsized systems. [ABSTRACT FROM AUTHOR]

Abstract: The impact of small amounts of carboxyl-functionalized multi-walled carbon nanotubes (MWCNT-COOH) added into a polyether-based thermoplastic polyurethane elastomer (TPU) was studied considering mainly on the morphological, mechanical, electrical and electrostrictive properties. The electrostrictive properties were measured by the analysis of the deformation response occurring under external electric fields E applied on 50μm-thick films. Dielectric measurements were carried out in order to determine the percolation threshold fc , which was found near 1v% loading. This volume fraction leads to a very high dielectric permittivity up to ≈330, i.e. about 50 times higher than that of the pure TPU, where . The thickness strain SZ and apparent electrostrictive coefficient M were measured at low electric fields, E ⩽4V/μm, by low frequency of 0.1Hz. The maximum induced-compressive strain was obtained from an optimal volume fraction of 0.8v% which yielded to a high Sz =11.5%, corresponding to almost a threefold increase of M compared to the neat TPU. Beyond fc , the conductivity sharply raised up and thus the electrostrictive activity disappeared. [Copyright &y& Elsevier]

Abstract: The electrostrictive properties of a polyether-based polyurethane elastomer and its corresponding composites filled with conductive carbon black (CB) were studied by measuring the thickness strain SZ induced by external electric fields E. For films with thicknesses of approximately 50μm, the apparent electrostrictive coefficient M was measured at low electric fields, E ⩽4V/μm, and different CB contents (up to a volume fraction of 2%). Dielectric measurements in AC mode were performed in order to determine the percolation threshold fc , which was 1.25v%. This optimal volume fraction yielded a remarkable threefold increase in M, associated with an increase of the dielectric constant by a factor 7, in comparison with pure PU. This enhancement of the electric field-induced strain and apparent electrostriction was mainly triggered by an increase of the dielectric constant, even if the intrinsic electrostriction coefficient Q was decreased. The nanocomposites thus seem to be very attractive for low-frequency electromechanical applications. Above fc , their conductivity was raised and their electrostrictive activity lost. Finally, there is a good agreement between the experimentally determined dependence on the CB content of the M coefficient and the theoretical estimation calculated from dielectric and mechanical measurements. [Copyright &y& Elsevier]

Abstract: This paper discusses the electromechanical potential improvement of polyurethane (PU) composite films by incorporation of carbon nanopowder in the polymer matrix. The beneficial influence on the electric field-induced is firstly measured and discussed. The observed non-linear mechanical behaviour of both pure PU elastomer and carbon/PU composite is described using constitutive hyperelastic Ogden Model. Finite Element Modeling with hyperelastic elements confirm the validity of the chosen model, assuming that actuation pressure is only due to electrostatic (Coulomb) forces at the electrodes. It also allows to predict the strain and stress distributions in the polymer films and the influence of the electrode size. Finally, mechanical performances of pure PU and composite C/PU disk actuators are compared in terms of strain energy density and actuation pressure under quasistatic state (non-linear actuator behaviour). The C/PU actuator exhibits an output mechanical energy increased by 50% compared to pure PU. [Copyright &y& Elsevier]

Abstract: In this study, some structural and electrical properties of a PZT base composition Pb0.89(Ba, Sr)0.11(Zr0.52Ti0.48)O3 co-doped with 1mol% manganese and 2mol% fluorine have been studied. Two different fluorine sources were used: lead fluoride PbF2 and manganese fluoride MnF2. These fluoride salts are added to the co-precipitated precursors powder. Mn dopant was added to the solution as manganese acetate (MnAc) before co-precipitation, when PbF2 was used. The structural analysis of the sintered ceramics revealed that MnF2 doping makes the volume of the cubic unit cell (V c) and the grain size decrease, whereas (MnAc, PbF2) co-doping makes the apparent density increase and keeps the average grain size and V c unchanged. Both types of doping reagents largely enhance the piezoelectric activity (high d 33 and k 33 coefficients, well saturated Polarization–Electric field loops) but MnF2 induces both combinatory soft and hard characteristics compared to (MnAc, PbF2) co-doping. Impedance spectroscopy showed that both types of doping reagents strongly reduce the electrical conductivity with the same conducting species, i.e. the same defect chemistry, confirmed by optical absorption data. Finally, this study shows that in the semi-wet process used, PbF2 is added homogeneously to the co-precipitated powder. Whatever the fluorine source, only the coexistence of Mn and F dopants is necessary to improve the piezoelectric response. [Copyright &y& Elsevier]

Abstract: In this study, ac and dc conductivity measurements were performed under ambient atmosphere on doped lead zirconate titanate (PZT) ceramics in order to investigate the defect chemistry by identifying the predominant charge carriers. The considered compositions were acceptor (1%mol Mn or Mg) and donor (Nb or F) co-doped PZTs with [Donor]=1 or 2%mol. The influence of donor concentration on the conductivity was determined. From the conduction activation energy values calculated in the temperature range 200–700°C, the principal contributing charge carriers are doubly-ionized oxygen and lead vacancies V Pb. For Mg doped PZTs, neither Nb nor F co-doping strongly reduce both conductivity levels and the dominant conducting species . For Mn doped materials, both donor co-dopants niobium and fluorine reduce the conductivity but do not have the same effect on the conduction mechanism at low temperature. With 2% Nb doping, the dominant conducting species are whereas electrical conduction is controlled by electrons from the second-ionization of oxygen vacancies with 2% F doping. The difference of oxygen vacancies content in (Mn, F) and (Mn, Nb) co-doped PZTs may be at the origin of the two distinct conducting species and of the different conductivity levels. [Copyright &y& Elsevier]

A magnetoelectric coupling in a low-cost and commercially available piezoelectric unimorph diaphragm is demonstrated by measuring magnetically induced AC voltage from the sample. Such a magnetoelectric effect could be achieved only because of the combination of magnetic forces within the electrodes and piezoelectric effect, without any magnetic constituent. Harvested magnetic power density across an optimal resistive load is found to be 0.12 mW/Oe.cm3 at the bending mode resonance frequency. The proposed transduction mechanism opens new and simple ways for producing electricity from stray magnetic fields. [ABSTRACT FROM AUTHOR]

Here, we report on a magnetoelectric (ME) coupling in a simple piezoelectric unimorph bender induced by the eddy currents within the silver electrodes of the piezoelectric ceramic Pb(Zr,Ti)O3 (PZT) subjected to ac magnetic flux. Eddy currents and the applied magnetic field generate Lorentz forces in the metal electrode acting on the PZT. A magnetically induced piezoelectric current linear versus dc magnetic biases is obtained at the ceramic electrodes. ME coupling is finally achieved with only one piezoelectric bender: (i) no magnetic phase is required, (ii) no ac current supply is necessary, eddy currents in electrodes are sufficient to generate Lorentz forces. [ABSTRACT FROM AUTHOR]

Abstract: This letter reports on the influence of piezomagnetic loss in magnetostrictive Terfenol-D (TeD)/polyurethane composite layer/piezoelectric PZT ceramic layer laminates on the phase shift between magnetoelectric current and ac magnetic field versus bias dc field. For a given low measurement frequency (1kHz), piezomagnetic losses are predominant when the amount of TeD powder embedded in polyurethane is small (2vol.%), inducing an imaginary magnetoelectric susceptibility and a 0° up to 180° variation of phase shift of magnetoelectric current. When TeD content is high enough (7vol.%), piezomagnetic losses are almost null, which yields a real magnetoelectric susceptibility and a −90° up to +90° variation of phase angle of the current. [Copyright &y& Elsevier]

We report the use of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as a transducing material in the fabrication of mechanical-to-electrical conversion devices based on the flexoelectric-like response of this polymer. Devices are made in a cantilever-based three-layer stainless-steel/PEDOT:PSS/top metal electrode configuration to assess the effective transverse flexoelectric coefficient μ 12 ′ . We investigated the influence of the nature of the top electrode in the flexoelectric response comparing samples with gold and aluminum top electrodes and demonstrated the huge impact of adding a small fraction of a second dopant such as xylitol to the PEDOT:PSS polymer blend and the benefits of a post-treatment of the polymer film with ethanol and methanol on the flexoelectric coefficient. The combination of xylitol addition and the rinsing of the polymer films with ethanol and methanol, along with the use of gold as a top electrode, led to a significant improvement of μ 12 ′ to ca. 24 μC m−1, which is in the range of those reported for high permittivity oxide materials. These findings support the use of conjugated polymers as an alternative to inorganic materials in flexoelectric-based applications, where large flexibility is required. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a quadratic electric field dependence of the strain on the −30kV corona-charged cellular polypropylene (PP) was observed, which was found to mainly originate from electrostriction after evaluation of Maxwell stress effect. The −30kV-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. [Copyright &y& Elsevier]

Abstract: Harvesting systems capable of transforming dusty environmental energy into electrical energy have attracted considerable interest throughout the last decade. Several research efforts have focused on the transformation of mechanical vibration into electrical energy. Most of these research activities refer to classical piezoelectric ceramic materials, but more recently piezoelectric polymer materials have also been considered. The goal of this paper has been to develop of a model capable of predicting the electrostrictive coefficient of EPCs. The model was developed by using the vibration transmission theory of a Euler–Bernoulli cantilever beam. After validating the model, at the macroscopic level, an empirical relationship was established predicting the value of the electrostrictive coefficient from the dielectric constants and the compliance coefficient of the material. The final results indicated that the dielectric constant was the crucial parameter, for the energy harvesting. [Copyright &y& Elsevier]

Abstract: The main objective of the paper is to point out the influence of composition and of poling state (poled and unpoled samples) on the evolution of various parameters (ɛ r, dilatation coefficients, lattice parameters) at different scales (lattice, bulk) using X-ray diffraction (XRD), thermo-mechanical analysis (TMA) and dielectric methods. The transition temperatures have been determined from the above measurements and compared. The composition has an influence on the transition temperature and not on the dilatation coefficient value. The poling state influences only the macroscopic dilatation evolution and not the value of the transition temperature. A scale effect is only observed on majoritary tetragonal compositions which show different values of transition temperatures from microscopic and macroscopic methods. [Copyright &y& Elsevier]

Ferroelectric single crystals of PZN–PT and PMN–PT exhibit outstanding properties: high charge coefficient (dij), high coupling factor (kij) and high strain levels under DC fields.Besides, their mechanical quality factor is believed to be low. Their usefulness for non-resonant or large bandwidth transducers has therefore been previously investigated.However, few studies have been devoted to the dielectric and mechanical losses of single crystals and to their stability under high levels of excitations (electric fields, temperature and mechanical stress). A knowledge and understanding of such performances is needed to determine whether single crystals are suitable materials for power or resonant transducers.In this work, losses and non-linearity versus external excitations are investigated. Dielectric losses and mechanical losses are measured versus electric field for different compositions, orientations.The evolution of d33 and ϵT33 are obtained versus electric field and temperature for the longitudinal mode. Strain and hysteresis versus sweep mode (up and down) are measured near the resonance frequency using a laser Doppler vibrometer. [Copyright &y& Elsevier]

Abstract: Particulate polymer composites consisting of Terfenol-D/Polyurethane, Fe3O4/Polyurethane, Nickel/Polyurethane and particulate composite layers were prepared by using a simple solution cast method. Magnetoelectric (ME) effect is characterized by measuring the amplitude of the magnetoelectric current versus different input parameters that appear in the theoretical current expression. The results yield two conclusions: 1.Whatever the filler type (Terfenol-D, Fe3O4 or Nickel), the microcomposites show a magnetoelectric effect. 2. The magnetostrictive property of the material does not have a direct influence on the ME effect since ME sensitivity is dc field independent and the magnetoelectric coefficient α p has close values in ac field for all types of polymer fillers. [Copyright &y& Elsevier]

Nonpercolated composites based on polyurethane (PU) filled with low concentrations copper (Cu) powders of varying sizes were studied as electrostrictive materials for mechanical energy harvesting. The dispersion of the fillers within the polymeric matrix was investigated by scanning electron microscopy, and results showed a relatively homogeneous dispersion for the microsized fillers and the existence of agglomerates for their nanosized counterparts. Differential scanning calorimetry measurements displayed that there occurred no interaction between the polymeric matrix and the microsized fillers whereas the nanosized fillers slightly enhanced the glass transition of the soft segments of PU and significantly affected the recrystallization temperature. The dependence of the dielectric properties of the composites as a function of the filler volume fraction and filler size was investigated over a broad range of frequencies, showing an increase in the permittivity when fillers were used. This increase was more pronounced for the composites containing nanosized fillers. The measurement of the harvested current and of the harvested power also demonstrated an enhancement of the energy harvesting capability when nanofillers were employed. From the experimental data, it appeared that the electrostrictive coefficient Q was not proportional to the inverse ratio of the permittivity and the Young modulus for the studied composites. Finally, analytical modeling of the harvested current and of the harvested energy offered an accurate description of the experimental data. [ABSTRACT FROM AUTHOR]

Electrostrictive polymers have demonstrated an ability to convert mechanical energy into electrical energy and vice versa. This energy conversion has been exploited in an extensive range of applications, including sensors and actuators. Recently, electrostrictive polymers have been investigated as electroactive materials for energy harvesting. The present work aims at establishing an analytical modeling based on electrostrictive equations for predicting a current that can be obtained from the first flexural mode of a beam which was attached by the electrostrictive polymers. The study was carried out on polyurethane films, either without filler or filled with nanosized SiC or a carbon nanopowder. Experimental measurements of the harvested current have been compared to the theoretical behavior predicted by the proposed model. A good agreement was observed between the two sets of data, which consequently validated that the modeling can be used to optimize the choice of materials. It was also shown that the incorporation of nanofillers in polyurethane increased the obtained current. [ABSTRACT FROM AUTHOR]

The influence of (Mn, F) and (Mg, F) dopants on the piezoelectric properties of lead zirconate titanate (PZT) ceramic compositions close to the morphotropic phase boundary is investigated. PZT ceramics are prepared by a chemical route based on co-precipitation of oxalates and hydroxides. The acceptor is incorporated into the B site of the materials and the fluorine ion is introduced into anionic sites. The d[SUB33] coefficient, the mechanical quality factor Qm and other properties are measured. Scanning electron microscopy is used to determine the grain size of the materials. Electron spin resonance is used to determine the valency state of Mn in fluorinated PZT ceramics. In Mn doped PZT, the introduction of a fluorine ion makes the poling process easier and increases the piezoelectric coefficients whereas the fluorination of Mg doped PZT constantly leads to hard materials with a lower piezoelectric response. This study shows that (Mn, F) co-doping produces semihard materials with high piezoelectric coefficients. [ABSTRACT FROM AUTHOR]

Electro-optic (EO) polymers offer a very attractive possibility of realizing low-cost microwave photonic components with a wide bandwidth and a low driving voltage, thanks to a low dispersion from microwave to optical frequency of polymeric materials on the one hand, and the progress in the synthesis of high hyperpolarizability chromophores on the other hand. This paper studies the influence of titanium dioxide (TiO) nanoparticle loading on the microwave and optical properties of EO polymers. Thus, poly(methyl methacrylate) (PMMA) and disperse red 1 (DR1) are used as host polymer and guest EO chromophore, respectively. With 1-3% TiO nanoparticle homogeneously incorporated in the polymer, the dielectric constant varies from 2.73 to 3.40 over the 400 MHz-10 GHz range, and the refractive index increases from 1.483 to 1.488 at the wavelength of 1539.6 nm. It is shown that fine tuning of dielectric constant and refractive index could allow improvement of the microwave photonic component bandwidth. For example, with an EO interaction length L = 2 cm (typical length of EO modulators), the ultimate modulator bandwidth could be raised to 258 GHz by loading PMMA-DR1 EO polymer with 1% wt of TiO nanoparticles. It is also found that loading polymer with nanoparticles could improve the EO response of poled polymers, represented by the intensity of the second-harmonic-generation (SHG) signal. The latter presents more than a threefold increase by loading PMMA-DR1 EO polymer with 2% wt TiO nanoparticles. [ABSTRACT FROM AUTHOR]

Pure polyurethane and nanocomposite carbon black (CB) polyurethane solutions were deposited by spin-coating on a silicon substrate using gold as the adhesion layer and electrode. Different test structures were achieved for electrical and mechanical characterizations. The incorporation of CB nanoparticles in the polyurethane matrix has a significant influence on the dielectric permittivity of the material with an increase of about one third of its value. The Young's modulus of PU and nanocomposite PU films was determined by different characterization methods. Nanoindentation experiments have pointed out a Young's modulus gradient through the film thickness. By performing mechanical tests (tensile, bulge, point deflection) on freestanding films, an average Young's modulus value of about 30 MPa was found as well as a residual stress value of about 0.4 MPa. However, no influence of the presence of the nanoparticles was found. Finally, several MEMS actuators were realized and characterized. At their fundamental resonance frequency, the actuation of the nanocomposite membranes is more efficient than that of pure polyurethane. However, the time constant of the material seems to provide a major barrier for the development of high-frequency PU-based micro-actuators. [ABSTRACT FROM AUTHOR]

Abstract: The study of the electrical properties of two-dimensional ferroelectric materials is very interesting because of the many possible applications relating to effects on their polarization properties. In this work we study the effect of a sinusoidal electric field on the dielectric and electrical properties of uni-axially and biaxially stretched polyvinylidene fluoride (PVDF) films. We have determined the polarization current, remanent polarization, maximal polarization, the hysteresis loop and coercive field as a function of applied electric field amplitude. The most interesting effects are the electric field (E) dependences of the resistivity. It is shown that for the biaxially stretched PVDF sample, the resistivity is almost constant, whereas for the uni-axially stretched specimen, a large decrease of resistivity is observed. [Copyright &y& Elsevier]

Abstract: The formation of barium titanate powder by solid-state reaction and oxalate coprecipitation route is re-investigated by differential thermal analysis–thermo-gravimetry (DTA–TG) thermal analysis and high temperature X-ray diffraction (XRD). The temperature formation of the perovskite phase is lower for the chemical way than for the solid state one, and no intermediate product is detected. The obtained powder leads to ceramics with high dielectric and piezoelectric properties. For example the room temperature piezoelectric d 33 coefficient is 260pC/N (higher than the values usually published in the literature) and it shows a good stability under electrical solicitations. These properties make BaTiO3 (BT) a lead-free high performance material for piezoelectric applications. [Copyright &y& Elsevier]

Abstract: Relaxor ferroelectric 0.60Pb(Mg1/3Nb2/3)O3–0.40PbTiO3 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 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°C at the bottom of the ingot and 222°C at the top. The piezoelectric coefficient of oriented and poled <001> samples varies from 1500 to 250pC/N. [Copyright &y& Elsevier]