Systèmes de récupération d'énergie vibratoire large bande

Dans ce travail de thèse nous nous sommes intéressés principalement à la récupération de l'énergie mécanique et plus particulièrement l'énergie vibratoire. Cette technologie repose sur l'utilisation des transducteurs résonants, ces dispositifs permettent d'amplifier l'amplitude de vibration et donc de stocker d'avantage d'énergie mécanique dans le convertisseur à la résonance. La quantité de l'énergie en sortie du convertisseur chute lorsque la fréquence de vibration n'est plus égale à la fréquence de résonance, il est donc nécessaire d'assurer un asservissement de la fréquence de résonance de la structure de récupération d'énergie vibratoire sur la fréquence de vibration, si possible sur tout le spectre fréquentiel que couvre la source de vibration. L'objectif de la thèse est de proposer des solutions, à basse consommation, permettant d'assurer un ajustement dynamique en temps réel de la fréquence de résonance en fonction de la fréquence de vibration. Les travaux de cette thèse s'articulent autour de trois solutions : 1) Ajustement de la fréquence de résonance par application d'un champ électrique dans un matériau piézoélectrique 2) Ajustement de la fréquence de résonance par adaptation de la charge électrique d'un matériau piézoélectrique 3) Amplification du mouvement vibratoire par technique de rebond Une modélisation et optimisation à la fois de la plage de fréquence de fonctionnement et de la conversion mécano-électrique ont été réalisées. Trois structures ont été développées et testées et permettent de valider chacune des trois approches. Enfin, une électronique très basse consommation a été mise au point pour asservir en temps réel la fréquence de résonance sur la fréquence de la source de vibration et optimiser le taux d'énergie électrique extraite du système (pour maintenir un facteur de qualité de la structure optimum).The work of this thesis is focused on the mechanical energy harvesting. This technology is generally based on the use of resonant transducers. Such systems work efficiently when their resonant frequency is equal to the vibration one. Otherwise, the output power from the harvester drops dramatically. Hence, it's necessary to ensure a continuous control of the resonant frequency of the harvester in order to avoid a possible shift between the resonant frequency and the vibration one, and doing this over the frequency spectrum covered by the vibration source. The main goal of this thesis is to develop new efficient solutions able to control in real time and tune the resonant frequency, these solutions should be low power consumption. During this thesis, three solutions have been developed: 1) adjustement of the resonant frequency by applying an electric field on the piezoelectric material; 2) adjustement of the resonant by adapting the electrical load; 3) the amplification of the structure relative displacement using a rebound technique. Modelling and optimization of both the frequency adjustment techniques and the mechanical-to-electrical conversion were performed. Three structures have been developed, tested and used to validate the three approaches. Finally, a very low power consumption electronic has been developed for a real time control of the resonant frequency, by regarding the vibration frequency, and also to optimize the extracted electrical energy from the harvester by maintaining an optimum quality factor.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Piezoelectricity in hafnia

Because of its compatibility with semiconductor-based technologies, hafnia (HfO2) is today’s most promising ferroelectric material for applications in electronics. Yet, knowledge on the ferroic and electromechanical response properties of this all-important compound is still lacking. Interestingly, HfO2 has recently been predicted to display a negative longitudinal piezoelectric effect, which sets it apart from classic ferroelectrics (e.g., perovskite oxides like PbTiO3) and is reminiscent of the behavior of some organic compounds. The present work corroborates this behavior, by first-principles calculations and an experimental investigation of HfO2 thin films using piezoresponse force microscopy. Further, the simulations show how the chemical coordination of the active oxygen atoms is responsible for the negative longitudinal piezoelectric effect. Building on these insights, it is predicted that, by controlling the environment of such active oxygens (e.g., by means of an epitaxial strain), it is possible to change the sign of the piezoelectric response of the material

Piezoelectricity in hafnia

Because of its compatibility with semiconductor-based technologies, hafnia (HfO2) is today’s most promising ferroelectric material for applications in electronics. Yet, knowledge on the ferroic and electromechanical response properties of this all-important compound is still lacking. Interestingly, HfO2 has recently been predicted to display a negative longitudinal piezoelectric effect, which sets it apart from classic ferroelectrics (e.g., perovskite oxides like PbTiO3) and is reminiscent of the behavior of some organic compounds. The present work corroborates this behavior, by first-principles calculations and an experimental investigation of HfO2 thin films using piezoresponse force microscopy. Further, the simulations show how the chemical coordination of the active oxygen atoms is responsible for the negative longitudinal piezoelectric effect. Building on these insights, it is predicted that, by controlling the environment of such active oxygens (e.g., by means of an epitaxial strain), it is possible to change the sign of the piezoelectric response of the material

Birefringence induced by antiferroelectric switching in transparent polycrystalline PbZr0.95Ti0.05O3PbZr_{0.95}Ti_{0.05}O_{3} film

The most characteristic functional property of antiferroelectric materials is the possibility to induce a phase transition from a non-polar to a polar phase by an electric field. Here, we investigate the effect of this field-induced phase transition on the birefringence change of $PbZr_{0.95}Ti_{0.05}O_{3}$. We use a transparent polycrystalline $PbZr_{0.95}Ti_{0.05}O_{3}$ film grown on $PbTiO_{3}/HfO_{2}/SiO_{2}$ with interdigitated electrodes to directly investigate changes in birefringence in a simple transmission geometry. In spite of the polycrystalline nature of the film and its moderate thickness, the field-induced transition produces a sizeable effect observable under a polarized microscope. The film in its polar phase is found to behave like a homogeneous birefringent medium. The time evolution of this field-induced birefringence provides information about irreversibilities in the antiferroelectric switching process and its slow dynamics. The change in birefringence has two main contributions, one that responds briskly (~ 0.5 s), and a slower one that rises and saturates over a period of as long as 30 minutes. Possible origins for this long saturation and relaxation times are discussed.Comment: 15 pages, 5 figure

Direct Visualization of Anti-Ferroelectric Switching Dynamics via Electrocaloric Imaging

The large electrocaloric coupling in PbZrO allows using high-speed infrared imaging for visualizing anti-ferroelectric switching dynamics via the associated temperature change. It is found that in ceramic samples of homogeneous temperature and thickness, switching is fast due to the generation of multiple nucleation sites, with devices responding in the millisecond range. By introducing gradients of thickness, however, it is possible to change the dynamics to propagation limited, whereby a single-phase boundary sweeps across the sample like a cold front, at a speed of ≈20 cm s. Additionally, introducing thermostatic temperature differences between two sides of the sample enables the simultaneous generation of a negative electrocaloric effect on one side and a positive one on the other, yielding a Janus-like electrocaloric response.The authors acknowledge financial support to ICN2, which is funded by the CERCA programme/Generalitat de Catalunya and by the Severo Ochoa programme of the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, Grant No. SEV-2017-0706). The authors also acknowledge the support of Plan Nacional (MINECO, Grant Nos. MAT2016-77100-C2-1-P and BES-2016-077392), as well as the Agencia Estatal de Investigacion (Grant No. PID2019-108573GB-C21). R.F. and E.D. thank the Luxembourg National Research Fund (FNR) for funding part of this research through the projects CAMELHEAT/C17/MS/11703691/Defay. This work was also supported in part by the Spanish Ministry of Science, Innovation and Universities under the HIPERCELLS project (RTI2018-098392-B-I00), the Regional Government of the Generalitat de Catalunya under Grant Nos. 2017 SGR 1384 and 2017 SGR 00579. This work was also supported by the National Science Centre, Poland, within the Project No. 2016/21/B/ST3/02242

Measuring lead scandium tantalate phase transition entropy by infrared camera

Using an infrared camera, we measured the latent heat of the first order phase transition in lead scandium tantalate at different applied electric fields. The entropy change value of 3.4 J kg_ 1 K_ 1 is consistent with differential scanning calorimetry measurements. The advantage of such an approach stems from the possibility to obtain both adiabatic temperature change and latent heat of the phase transition material only with an infrared camera or a thermocouple. This may prove useful for a systemic characterization of first order electrocaloric materials

Origin of the Large Negative Electrocaloric Effect in Antiferroelectric PbZrO3

We have studied the electrocaloric response of the archetypal antiferroelectric PbZrO3 as a function of voltage and temperature in the vicinity of its antiferroelectric-paraelectric phase transition. Large electrocaloric effects of opposite signs, ranging from an electro-cooling of -3.5 K to an electro-heating of +5.5 K, were directly measured with an infrared camera. We show by calorimetric and electromechanical measurements that the large negative electrocaloric effect comes from an endothermic antiferroelectric-ferroelectric switching, in contrast to dipole destabilization of the antiparallel lattice, previously proposed as an explanation for the negative electrocaloric effect of antiferroelectrics.Comment: Article (17 pages) and supplemental material (12 pages) present in .pdf fil

Roadmap on energy harvesting materials

Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere

Ferroelectric dielectrics integrated on silicon

This book describes up-to-date technology applied to high-K materials for More Than Moore applications, i.e. microsystems applied to microelectronics core technologies.After detailing the basic thermodynamic theory applied to high-K dielectrics thin films including extrinsic effects, this book emphasizes the specificity of thin films. Deposition and patterning technologies are then presented. A whole chapter is dedicated to the major role played in the field by X-Ray Diffraction characterization, and other characterization techniques are also described such as Radio frequency characteriza