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Antiferroelectric lead zirconate titanate (PZT) thin films have been prepared by chemical solution deposition using oxide powders. The films were processed onto steel substrates coated with a conducting oxide layer of LaSrMnO3. Homogeneous and uniform films up to 3.4 μm thick and with polarization saturation values up to 35 μC/cm2 have been obtained. The compositional transition from the ferroelectric to the antiferroelectric phase at the high zirconium side of the PZT phase diagram was studied by x-ray diffraction and hysteresis loop measurements as a function of the Zr/Ti ratio. Film thickness and annealing temperature dependencies are reported.

The conversion of vibrations into electrical energy for powering low-power small electronic components has been investigated by researchers from different disciplines in the last decade. Among the possible mechanisms, piezoelectricity has received particular attention. In the field of low frequency cantileverbased vibration energy harvesters, the proof mass is essential in order to reduce the resonance frequency and increase the stress along the beam to increase the output power. In this work, a manufacturing process of a micro generator is proposed to easily modify and increase the dimensions of the cantilever, and thus tune its resonance frequency. The effect of the position of the mass on the performances of this flexible piezoelectric energy harvester is also studied. For a proof mass at 8 cm from clamping, we obtain a resonance frequency of 9.9 Hz, a maximum power of 127 μW against a resonance frequency of 16 Hz and a maximum power of 72 μW with a mass at 4 cm. This shows that the maximum power extracted varies in for a constant acceleration of 1 g (9.81 m/s 2 ), as expected theoretically. These ≅ 1 ! promising results show that the prototype can be considered for a low power application as an energy harvesting-based micro-generator.

International audienceLead zirconate titanate (PZT) thin films with a Zr/Ti ratio of 57/43, elaborated by a derived sol-gel process, have been deposited onto bare and RuO2 coated aluminium substrate 16 μm thick. Commercial aluminium foil presents many advantages as ultra light weight (43 g m−2), conformability, conduction, can be easily cut, and is one of the cheapest substrates used for PZT thin films deposition (<0.1$ m-2). XRD measurements have shown a well crystallized PZT in the perovskite structure and ferroelectric behaviour has also been observed. By the use of a RuO2 film 100 nm thick at the PZT/aluminium interface, the coercive field and tunability values have been strongly improved despite an increase of the dielectric losses. The lead excess introduced in the precursor solution has been increased up to 65 % in order to lower the crystallization temperature of the PZT around 560 °C and tunability has been studied as a function of annealing time and temperature

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 350 μm. 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 μ12′ with the decreasing film thickness was found, especially for thicknesses lower than 25 μm. The variation of μ12′ 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 80 m−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.