Ce travail a pour objectif la détermination des propriétés fonctionnelles des matériaux piézoélectriques : les coefficients de couplage, les constantes élastiques, piézoélectriques et diélectriques, de même que les pertes électriques et mécaniques. De nos jours, les techniques conventionnelles d’identification de ces paramètres utilisent plusieurs échantillons. Dernièrement le laboratoire a développé (Delaunay et al.) une méthode ultrasonore de caractérisation de matériaux piézoélectriques permettant de déterminer ces propriétés à partir d’un seul échantillon. Cette méthode, basée sur la spectroscopie de résonance ultrasonore, examine les modes de vibrations d’un cube piézoélectrique et extrait des résonances mécaniques mesurées par interférométrie Laser les propriétés électromécaniques de l’échantillon. Dans ce travail, cette méthode a été modifiée afin d’obtenir les propriétés électromécaniques des matériaux à partir d’une seule mesure d’impédance électrique. Dans un premier temps, le problème direct est résolu ; les fréquences propres et les modes propres d’un cube sont modélisés par une méthode variationnelle ; les champs de déplacement et l’admittance électrique sont calculés en fonction de la fréquence. La géométrie étant fixée, forme cubique, l’admittance dépend seulement des propriétés du matériau et des conditions de métallisation de l’échantillon. La méthode est validée à travers la caractérisation d’un cube de PMN-34,5PT dont les propriétés sont connues. Les mesures électriques de l’impédance de l’élément sont comparées au spectre d’admittance prédit par la théorie. Les vitesses de vibration du matériau sont également mesurées et comparées aux résultats donnés par les modèles existants. La résolution du problème inverse, permet de déterminer les propriétés d’un matériau inconnu, à travers la convergence de courbe d’admittance théorique vers celle expérimentale. Les propriétés du PZ-21 sont extraites grâce à cette procédure. Une discussion sur ces valeurs et une comparaison avec celles de la littérature permet de valider les résultats obtenus. / This work deals with the determination of electromechanical properties of piezoelectric materials: coupling coefficients, elastic, dielectric and piezoelectric constants, electrical and mechanical losses. Until now, several samples are needed in conventional techniques to perform the complete identification of the material properties. Recently, Delaunay et al. proposed an ultrasonic protocol allowing the determination of these characteristics from only one sample. This method, referred to as Resonant Ultrasound Spectroscopy, is based on the comparison of the mode shapes and frequencies of modeled vibration modes of piezoelectric parallelepipeds with experimental data measured by Laser interferometry. It is here modified to obtain the electromechanical properties from electrical impedance measurements only. The direct problem is first solved: the resonance modes of a two face metalized piezoelectric cube are modeled and both mechanical displacements and electrical impedance are calculated as functions of the frequency. The method is first applied for validation on a PMN-34.5PT material with known properties. Electrical impedance and mechanical velocity measurements are performed and their agreement to the theoretical predictions is discussed. In order to determine the properties of unknown materials, the inverse problem is solved by fitting the theoretical impedance curves to experimental ones. This procedure is then applied to the identification of the properties of PZ-21. The results are discussed and compared to data from the literature.

abstract: Despite the growth of technology in music composition and performance, professional clarinetists maintain that air microphones are superior to piezoelectric pickups. Pickups offer increased mobility, isolation, and reduced feedback, but air microphones are used simply for the perceived sound quality. In this study a ported barrel pickup and a contact transducer pickup placed at various intervals on the clarinet were sampled and compared to a reference recording to determine how the sound differed for each method. In addition, the history of wind instrument pickups, the acoustics of the clarinet, and the basics of piezoelectricity were discussed to help examine the results. The pickups were examined in three ways: overall level in decibels, frequency cutoff, and overtone displacement. Through these results it was determined that the most accurate methods of clarinet pickup are the ported barrel pickup, contact transducers closer to the vibration of the reed such as the ligature or barrel surface, or a transducer placed at the end of the bell. These findings were consistent with the discussions regarding history, clarinet acoustics, and piezoelectricity. This study also produced a reference for the sounds associated with different pickup methods, as well as possible improvements for clarinet pickup design. / Dissertation/Thesis / Doctoral Dissertation Music 2018

Les matériaux piézoélectriques ont été étudiés en détails du fait de la versatilité des applications industrielles possibles (accéléromètres, gyroscopes ou transducteurs). Les bonnes propriétés piézoélectriques (d33=510pC/N) de Pb(Yb½Nb½)O₃-PbTiO₃ (PYN-PT) et sa haute température de Curie (~370°C à la MPB). Cette solution solide entre une double pérovskite (ordonné sur le site B) et le titanate de plomb est remarquable, du fait qu'elle présente tous les ordres polaires à température ambiante: antiferroélectricité, ferroélectricité et des propriétés relaxeurs.Dans le cadre de ce travail de thèse, je présente les résultats obtenus sur des céramiques de PYN-PT de diverses compositions à travers le diagramme de phase. A partir des mesures de diffractions de rayons X et de diffusion neutronique, de spectroscopie diélectrique ainsi que des mesures piézoélectriques et ferroélectriques, un nouveau diagramme de phase sera proposé.Cette étude minutieuse du diagramme de phase a montré que celui-ci est plus compliqué que ce que laissait apparaître la littérature. En particulier, la structure de l'antiferroélectrique PYN est particulière en comparaison des autres pérovskites antiferroélectriques au plomb. En effet, dans PYN, les atomes de plomb sont déplacé suivant la direction du vecteur de modulation et les cations B sont en dehors de leurs positions prototypiques et participe à l'ordre antipolaire observé.De plus, la zone morphotropique (x _0.50) s'étale sur une zone en compositions beaucoup plus grande que ce qui a été observé dans d'autres solutions solides à base de plomb. Dans la zone pauvre en PT de la zone morphtropique, l'absence de phase rhomboédrique (attendue par analogie avec les autres systèmes au plomb) a été démontré.D'autre part, parmi les compositions présentant des propriétés relaxeurs, des différences sont apparues et il est proposé que, dans la solution solide PYN-PT, plusieurs types de relaxeurs existent.Finalement, je propose un modèle expliquant continument le changement d'ordre polaire dans le diagramme de phase. Ce modèle est basée sur la corrélation des déplacements de plomb induite par la nature chimique et l'arrangement cationique du site B. / Piezoelectricity has attracted a considerable amount of work due to the variety of possible applications such as accelerometers, gyroscopes or transducers. Pb(Yb½Nb½)O₃-PbTiO₃ is long known to have large piezoelectric properties (d33=510pC/N) and a relatively high Curie temperature (_370°C at the MPB).This solid solution between a double (B-site ordered) perovskite (Pb2YbNbO6) and lead titanate is remarkable, in the sense that it presents all polar orders. Indeed, depending on the composition, the solid solution can exhibit at room temperature: antiferroelectric, classical ferroelectric or relaxor properties. In this work, I will present results obtained on PYN-PT ceramics of various compositions spanning the phase diagram. From experiments using X-ray diffraction and neutron scattering, dielectric spectroscopy, as well as piezoelectric and ferroelectric measurements as a function of temperature, a new phase diagram is proposed. This thorough study of the phase diagram of PYN-PT has revealed a more complex phase diagram than what was reported in the literature. In particular, the structure of the antiferroelectric PYN is peculiar compared to the other Pb-based antiferroelectric. Indeed, in PYN, the Pb atoms are displaced along the direction of the modulation vector and that the B cations are not in their prototypic positions and take part in the antipolar order observed.Moreover, the morphtropic phase boundary (x _0.50) extends over a larger compositional range than what was observed in other Pb-based solid solution. In the PT-poor side of the morphtropic phase boundary, the absence of the expected rhombohedral phase (by analogy with the other Pb-based solid solutions) was demonstrated. Furthermore, among the compositions presenting relaxor properties, differences have arisen and I suggest that several types of relaxors exist, in the PYN-PT solid solution. Finally, I will propose a model explaining continuously the change of polar order through out the phase diagram. This model is based on the correlation of Pb displacements induced by the chemical nature and the cationic arrangement on the B site.

Piezotech, une start-up rachetée en 2010 par le leader français de la chimie, Arkema, développe et commercialise des copolymères fluorés électroactifs (EAPs). Ces copolymères présentent un grand intérêt pour des applications dans l’électronique imprimée, les capteurs, les actionneurs, les muscles artificiels, et le stockage de l’énergie. Les copolymères à base de fluorure de vinylidène (VDF) et de trifluoroéthylène (TrFE) possèdent les meilleures propriétés piézoélectriques et ferroélectriques (FE) parmi les polymères existants. L’introduction d’un termonomère, tel que le 1,1-chlorotrifluoroéthylène (CFE) ou le chlorotrifluoroéthylène (CTFE), modifie la conformation de la chaine polymère et change le comportement du matériau en relaxeur ferroélectrique (RFE). Le travail de thèse s’inscrit dans la recherche de nouveaux EAPs fluorés et la compréhension des relations structure-propriétés de ces matériaux. Après l’étude de la cinétique de copolymérisation avec le VDF et le TrFE de différents termonomères porteurs de groupements CF3, les terpolymérisations ont été examinées. Dans une première partie, le trans-1,3,3,3-tetrafluoropropène (1234ze), un termonomer qui n’homopolymérise pas, a été étudié. Des terpolymères de composition homogène ont été synthétisés. Ensuite, le 3,3,3-trifluoropropène (TFP) et le 2,3,3,3-tetrafluoropropène (1234yf) ont été terpolymérisés avec le VDF et le TrFE. Bien que les terpolymérisations batch amènent à une forte dérive de composition, un procédé de polymérisation en suspension en semi-continu a permis d’obtenir une meilleure homogénéité. Les propriétés thermiques et électroactives de tous les terpolymères ont été caractérisées. Dans une dernière partie, l’introduction d'une faible quantité d’un monomère fonctionnel (2-(trifluorométhyl) acide acrylique, MAF), dans les chaines du copolymère poly(VDF-co-TrFE), a permis une amélioration des propriétés d’adhésion sur le verre et le métal sans altérer les propriétés électroactives. L’étude des terpolymérisations avec le VDF, le TrFE et un termonomère porteur d’un groupement CF3 a contribué l’amélioration de la compréhension des relations structure-propriété dans les EAPs fluorés. En particulier, il a été montré que la réduction de la taille des cristaux n’est pas une condition suffisante pour obtenir un caractère RFE. / Piezotech, a start-up acquired in 2010 by the French leader in Chemistry, Arkema, develops and commercializes fluorinated electroactive copolymers (EAPs). These copolymers arouse a significant interest in printed electronics, printed memories, sensors, actuators, artificial muscles, and energy storage devices. Vinylidene fluoride (VDF) and trifluoroethylene (TrFE) -based copolymers are the polymers exhibiting the highest piezoelectric and ferroelectric (FE) properties. The introduction of a third slightly bulkier termonomer such as 1,1-chlorofluoroethylene (CFE) or chlorotrifluoroethylene (CTFE) was shown to modify the polymer chain conformation and change their electroactive behaviors into those of relaxor ferroelectric (RFE) materials. This PhD work aimed to discover new fluorinated EAPs and to better understand their structure-properties relationships. After the study of the kinetics of copolymerization of various CF3-bearing termonomers with VDF and TrFE; the terpolymerizations were investigated. First trans-1,3,3,3-tetrafluoropropene (1234ze), a non-homopolymerizable termonomer, was studied. Terpolymers with homogeneous compositions were synthesized. Then, 3,3,3-trifluoropropene (TFP) and 2,3,3,3-tetrafluoropropene (1234yf) were terpolymerized with VDF and TrFE. Although batch terpolymerizations resulted in terpolymers with strong compositional drift, the semi-continuous suspension process afforded better homogeneity. The thermal and electroactive properties of all the terpolymers were characterized. Finally, the introduction into poly(VDF-co-TrFE) copolymer chains of small amounts of a functional monomer (2-(trifluoromethyl)acrylic acid, MAF) allowed an increase of the adhesion properties onto glass and metal substrates without altering the electroactive properties. The study of the terpolymerizations of VDF, TrFE and a CF3-bearing termonomer contributed to a better understanding of the structure-properties relationships in fluorinated EAPs. Notably, the reduction of the crystal size was shown to be insufficient to afford RFE properties.

The crystal structure of caesium permanganate has been determined. CsMn0₄ crystallises in the orthorhombic space group Pnma. There are four molecules per unit cell with a = 10.0692 Å, b = 5.8080 Å, c = 7.9470 Å. The structure was determined by Fourier syntheses on the (010) and (001) projections and refined by two-dimensional difference syntheses. The structure is similar to that of KMn0₄. The manganese is surrounded by four oxygen atoms at an average distance of 1.629 Å arranged in a slightly distorted tetrahedron. The caesium is surrounded by eight manganese atoms at an average distance of 4.381 Å.

Piezoelectric nanogenerators (PNGs) are a new class of energy harvesting materials that show potential as a direct energy source for low powered electronics. Recently, piezoelectric polymers have been utilized for PNG technology due to low toxicity, high flexibility, and facile solution processing which provide manufacturing opportunities such as screen printing. Throughout the last decade, countless projects have focused on how to enhance the energy harvesting capabilities of these PNGs through the incorporation of nanoparticle fillers, which have been reported to enhance the piezoelectric properties of the film either directly through their intrinsic piezoelectric properties or through acting as surfaces for the interfacial nucleation of piezoelectric polymer crystals. Herein, two systems of PNGs formed from piezoelectric copolymers poly(vinylidene fluoride-co-hexafluropropylene) or poly(vinylidene fluoride-co-trifluoroethylene) mixed with high aspect ratio zinc oxide nanowires, hydroxyl functionalized multi-walled carbon nanotubes, or carboxylic acid functionalized single walled carbon nanotubes were investigated. Variations of filler type and loading are tested to determine influences on film morphology and piezoelectric properties. Power harvesting tests are conducted to directly determine the effect of nanoparticle addition on the output power of the non-poled devices. Both copolymer systems are found to exhibit a non-linear increase in output power with the increase of nanoparticle filler loading. The crystal polymorph properties of both systems are investigated by Fourier transform infrared spectroscopy. The microstructure of the poly(vinylidene fluoride-co-trifluoroethylene) films are further examined using X-ray diffraction, differential scanning calorimetry, polarized optical microscopy, and atomic force microscopy to determine the mechanism behind the increased power harvesting capabilities. As well, explanations for perceived output power from “self-poled” films are briefly explored.

Vibration energy harvesting has been widely investigated by academia and industry in the past decade with focus on developing distributed power sources. One of the prime goals of energy harvesters is to provide power to wireless sensors allowing for the placement of these sensors in the remote and inaccessible areas where battery is not an option. Electromechanical modeling approaches have been developed for enhancing the mechanical to electrical conversion efficiencies utilizing electromagnetic, piezoelectric, and magnetostrictive mechanisms. Models based upon the constitutive equations for these three conversion mechanisms, supported by extensive experimental results available in literature, suggest that power requirement through energy harvesters can be met only when the total volume is in the range of 1-100 cm3. There exists a critical volume of 0.5 cm³ at which above which the electromagnetic mechanism exhibits higher power density as compared to the other mechanisms. Therefore, in this thesis electromagnetic energy conversion was adopted to develop high power energy harvesters. We also present a novel vibration energy harvesting method which rivals the power density and bandwidth of the traditional methods. The overarching theme throughout the design process was selecting the structure and fabrication methodology that facilitates the transition of the technology. The experimental models were characterized at accelerations and frequencies typically found in the environmental vibration sources. The thesis provides in-depth the design, modeling, and characterization of a vibration energy harvester which creates relative motion differently than the conventional harvesters. Conventional designs rely on amplifying the original source displacement operating at the resonance condition. In the harvester design proposed in this thesis, the relative motion is created by cancelling the vibration at one location and transferring the source vibration directly to another location by combining a vibration isolator with a vibration absorber. In this novel configuration, termed as Direct Vibration Harvester (DVH), the energy is harvested directly from the vibrating source mass rather than a vibrating seismic mass attached to the source increasing the harvesting bandwidth and power density. Four bar magnet and magnetic levitation architectures were modified and modeled to reach closer to the theoretical maximum power densities. Extensive FEM was utilized to understand the performance limitations of the existing structures and the results from this analysis paved the pathway towards the development of the DVH. �A comparative analysis of the performance of the DVH with the traditional harvesting methods in terms of normalized power output and bandwidth was conducted. Performance improvements of DVH required development of the high efficiency rotational generators as linear to rotational conversion occurs in the DVH. The optimized rotational generator was modeled and all the predicted performance metrics were validated through experiments. The generator was applied towards the fabrication of DVH and also in a micro windmill. The power density of the micro windmill was found to be better than all the other results reported in literature. Extensive fluid and structural modeling was conducted to tailor the performance of the micro windmill in the desired wind speed range. Combined, this thesis provides significant advancement on many fronts. It pushes the magnetic levitation and four-bar mechanism harvester systems to their theoretical limits. It demonstrates a novel direct vibration harvester that has the possibility of surpassing the power density and bandwidth of all the known vibration harvester with large magnitude of output power. It provides a design process for an efficient small scale electromagnetic generator that can form for the backbone of many rotational and linear harvesters. This generator was used to develop the world's highest power density micro windmill in the small wind speed range. / Ph. D.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21777号 / 工博第4594号 / 新制||工||1716(附属図書館) / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 木村 俊作, 教授 瀧川 敏算, 教授 藤田 晃司 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

BACKGROUND: Piezoelectric surgery (PIEZO) uses ultrasonic vibration to cut hard tissue without damaging adjacent soft tissues. Our previous studies indicated that PIEZO enhanced bone turnover compared to a conventional rotary bur (BUR) in rat tibia wounds by inducing the regional acceleratory phenomenon (RAP). PIEZO induced osteocyte apoptosis without damaging blood vessels during Day 1, 3 and 7 of rat tibia healing. We hypothesized that PIEZO increased bone turnover by activation of osteocyte apoptosis with a controlled inflammatory response. This study evaluated early morphological changes in tibial defects caused by either PIEZO or BUR. MATERIALS & METHODS: We created surgical defects in tibia by either PIEZO or BUR in 9–10-week-old Sprague-Dawley rat tibias (n=4). We evaluated tissue responses by using H&E, Masson’s Trichrome and TRAP stains on Day 1, 3 & 7 after surgery. The surgical defect beneath the soft tissue was located using Computed Tomography (CT). RESULTS: On postoperative Day 1, there was no significant blood vessel change or cellular extravasation in the PIEZO group. In contrast the BUR group had extravasation of leukocytes and increased blood vessels' size. On Day3, there was no significant inflammation or morphological changes to blood vessels in the PIEZO group. Empty lacunae adjacent to the defect area suggested osteocyte apoptosis. In the BUR group, blood vessels returned to an average size and the leukocyte population was reduced and bone adjacent to the lesion was unaffected, and intact osteocytes were in the lacunae. On Day 7 there was increased in osteoclastic activity in Piezo compared the BUR group. CONCLUSION: These results suggested that PIEZO induced osteocyte apoptosis, increased bone turnover with a controlled inflammatory response and protected the bone blood vessel network.

A two-scale model consisting of ceramic grain scale and composite scale are developed to systematically evaluate the effects of microstructures (e.g., residual pores, grain size, texture) and geometry on the piezoelectric responses of the polarized triply periodic bi-continuous (TPC) piezocomposites. These TPC piezocomposites were fabricated by a recently developed additive manufacturing (AM) process named suspension-enclosing projection-stereolithography (SEPS) under different process conditions. In the model, the Fourier spectral iterative perturbation method (FSIPM) and the finite element method will be adopted for the calculation at the grain and composite scale, respectively. On the grain scale, a DL approach based on stacked generative adversarial network (StackGAN-v2) is proposed to reconstruct microstructures. The presented modeling approach can reconstruct high-fidelity microstructures of additively manufactured piezoceramics with different resolutions, which are statistically equivalent to original microstructures either experimentally observed or numerically predicted. Design maps for hydrostatic piezoelectric charging coefficients dh show they can achieve optimal performance at wide ranges of micro-porosity and geometry parameter u for the proposed TPC piezocomposites. In addition, geometry parameter u plays a dominant role in determining the intensity of hydrostatic voltage coefficient gh and hydrostatic figure of merit (HFOM) of all the presented TPC piezocomposites in the vicinity of the starting point of three-dimension (3D) interconnectivity. Within this range, these properties would increase first with the increasing of micro-porosity volume fraction (VF) and start to decrease once they reach peak values. The presented TPC piezocomposites exhibit a superb hydrostatic properties, with the same 20% VF of ceramics and 2% VF of micro-porosity with respect to composites and ceramics, respectively, TPC of face center cubic (FCC) demonstrates 327-fold enhancement of HFOM than that of the piezocomposite with three intersecting ceramic cuboids. The piezoelectric properties of FCC are superior to those of body center cubic (BCC) and simple cubic (SC). The calculated piezoelectric charging constants d33 and relative permittivity κ33 were then compared with the data measured from the products fabricated by the SEPS under different process conditions. The calculation results at both grain scale and composite scale were found to agree well with experimental results.