We propose a method to evaluate the Total Harmonic Distortion generated by a cantilever-based PZT loudspeaker inside an IEC 60318-4 coupler. The model is validated using experimental data of a commercial loudspeaker. Using the time domain equations of the equivalent electrical circuit of the loudspeaker inside the coupler and a state space formulation, the acoustic pressure response is calculated and compared to the measurement of the manufacturer. Next, the stiffness, transduction and capacitance nonlinear functions are evaluated with a Double-Beam Laser Interferometer (DBLI) and a nanoindenter on test devices and on the commercial loudspeaker. By introducing the nonlinear functions into the model as amplitude-dependent parameters, the THD generated by the loudspeaker is calculated and compared to the value provided by the manufacturer. The good agreement between the measurement and the simulation could allow for a rather quick simulation of the performance of similarly designed loudspeakers at the early stage of the design, by only estimating the static linearity of the main nonlinearity sources.

We present a study of the effect of electrically induced cracks on both the ferroelectric and piezoelectric properties of Pt/PbZr_0.52Ti_0.48O₃ (PZT)/Pt capacitors and correlations with domain structures of PZT films. Above a threshold bipolar electric field, cracks appear inside the PZT layer thickness leading to an increase in the ferroelectric polarization (+50% for the remnant polarization, from 16 to 25 μC/cm²) and the longitudinal piezoelectric coefficient d_33,f (from ∼150 to ∼220 pm/V). The use of x-ray diffraction during in situ biasing provides direct evidence for a modification of the PZT crystalline structure as well as the a/c domain configuration. After cracking, the fraction of c-domains is strongly increased, thus contributing to higher polarization and larger strain in the out-of-plane direction.

Switching Spectroscopy Piezoresponse Force Microscopy (SSPFM) stands out as a powerful method for probing ferroelectric properties within materials subjected to incremental polarization induced by an external electric field. However, the dense data processing linked to this technique is a critical factor influencing the quality of obtained results. Furthermore, meticulous exploration of various artifacts, such as electrostatics, which may considerably influence the signal, is a key factor in obtaining quantitative results. In this paper, we present a global methodology for SSPFM data processing, accessible in open-source with a user-friendly Python application called PySSPFM. A ferroelectric thin film sample of potassium sodium niobate has been probed to illustrate the different aspects of our methodology. Our approach enables the reconstruction of hysteresis nano-loops by determining the PR as a function of applied electric field. These hysteresis loops are then fitted to extract characteristic parameters that serve as measures of the ferroelectric properties of the sample. Various artifact decorrelation methods are employed to enhance measurement accuracy, and additional material properties can be assessed. Performing this procedure on a grid of points across the surface of the sample enables the creation of spatial maps. Furthermore, different techniques have been proposed to facilitate post-treatment analysis, incorporating algorithms for machine learning (K-means), phase separation, and mapping cross correlation, among others. Additionally, PySSPFM enables a more in-depth investigation of the material by studying the nanomechanical properties during poling, through the measurement of the resonance properties of the cantilever–tip–sample surface system.

K-enriched KNN target effectively prevents alkali cation deficiency, ensuring typical piezoelectric and ferroelectric behavior. In particular, it avoids the secondary phase K ₄ Nb ₆ O ₁₇ in KNN thin films obtained by PLD using a stoichiometric target.

L’interdiction de l’utilisation du plomb avec la norme RoHS menace l’utilisation du Titano-Zirconate de plomb (PZT) employé majoritairement en microélectronique dans les applications piézoélectriques actionneurs. Le (K,Na)NbO₃ (KNN) est un matériau prometteur pour le remplacer. L’objectif de cette thèse est d’évaluer comme matériau alternatif au PZT pour l’actionnement piézoélectrique. Des films monophasés de KNN pérovskite d'une épaisseur de 600 nm ont été déposés avec succès par ablation laser pulsée sur des substrats de dimensions centimétriques et sur des wafers de Silicium de 200 mm de diamètre. Des condensateurs piézoélectriques fonctionnels ont été réalisés et ont permis de démontrer le comportement piézo- et ferroélectrique de ces films. Un KNN commercial déposé par pulvérisation cathodique a été intégré selon un procédé industriellement compatible afin de réaliser des preuves de concepts de fonctionnement de dispositifs actionneurs à base de KNN (cantilevers et membranes). Les mesures de déflexion des cantilevers de KNN ont permis d’estimer un coefficient d₃₁ compris entre 100 et 150 pm/V. Une étude de fiabilité portant sur la résistance à la fatigue et aux claquages électriques a été menée sur ces wafers. Les condensateurs de KNN avaient une résistance au claquage inférieur en moyenne de 20 % à celle des condensateurs de PZT. Enfin une étude sur la fissuration de condensateurs de PZT a permis de corréler des variations de propriétés structurales avec les propriétés piézoélectriques.