Unified model for the electromechanical coupling factor of orthorhombic piezoelectric rectangular bar with arbitrary aspect ratio

Piezoelectric Single Crystals (PSC) are increasingly used in the manufacture of ultrasonic transducers and in particular for linear arrays or single element transducers. Among these PSCs, according to their microstructure and poled direction, some exhibit a mm2 symmetry. The analytical expression of the electromechanical coupling coefficient for a vibration mode along the poling direction for piezoelectric rectangular bar resonator is established. It is based on the mode coupling theory and fundamental energy ratio definition of electromechanical coupling coefficients. This unified formula for mm2 symmetry class material is obtained as a function of an aspect ratio (G) where the two extreme cases correspond to a thin plate (with a vibration mode characterized by the thickness coupling factor, kt) and a thin bar (characterized by k33′). To optimize the k33′ value related to the thin bar design, a rotation of the crystallogaphic axis in the plane orthogonal to the poling direction is done to choose the highest value for PIN-PMN-PT single crystal. Finally, finite element calculations are performed to deduce resonance frequencies and coupling coefficients in a large range of G value to confirm developed analytical relations

Matériaux piézoélectriques sans plomb pour transducteurs acoustiques

International audienceLes céramiques PZT sont utilisées pratiquement dans tous les dispositifs du fait de leur faible cout de production et de leur performance. Les excellentes propriétés piézo-électriques de ces oxydes perovskite complexes (PbZr x Ti y 0 3 ou PZT, PbMg 1/3 Nb 2/3 O 3 -PbTiO 3 ou PMN-PT,…) sont dues à la présence du plomb qui est un élément principal. Du fait de la politique sanitaire et environnementale relative à l'élimination du plomb dans les matériaux, l'alternative des céramiques sans plomb est une question à résoudre pour les industriels. L'inscription de PZT dans l'annexe 15 de REACH en décembre 2012 conduit à l'impératif projet de leur substitution. Cet exposé présentera l'état de l'art sur les matériaux piézoélectriques sans plomb et les pistes de travail des céramiques aux monocristaux et céramiques texturées. Les propriétés des matériaux à base de BaTiO 3 et K/NaNbO 3 issus des projets français seront comparées pour éclairer le potentiel de substitution. Quelques exemples des applications potentiels, LF Langevin transducteur et HF médical transducteur, seront présentés

Texturation of lead-free BaTiO3 based piezoelectric ceramics

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La texturation des céramiques : application aux matériaux piézoélectriques sans plomb

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Optimized self-consistent full database of piezoelectric material: application to KNbO3 single crystal

International audienc

Optimized self-consistent full database of piezoelectric material: application to KNbO3 single crystal

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Complete electroelastic set for the (YXt)-45 cut of a KNbO3 single crystal

International audienceA complete and consistent set (elastic, dielectric, and piezoelectric tensors) of a commercial lead-free (YXt)-45 cut KNbO 3 single crystal is reported. These data were obtained using several samples and the resonance-antiresonance method. Particular attention was paid to the consistency of this delivered database. A genetic algorithm with an appropriate criterion was used. Electromechanical characterization revealed a high thickness coupling factor of approximately 60%. These properties make this single crystal a good candidate for several applications such as medical imaging. This complete set provides a basis for simulation designs of such devices integrating this piezoelectric lead-free material, especially for ultrasonic transducers. V C 2014 AIP Publishing LLC

Texturation of lead-free BaTiO3 based piezoelectric ceramics

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