Julien Bustillo

Modelling of hysteretic behavior of piezoceramic materials under electrical loading

The purpose of this study is to model the hysteretic behavior of piezoceramic materials under electrical loading. Remanent strain and remanent polarization are chosen as internal variables. A domain orientation distribution is used to describe the evolution of these variables by bridging the characteristics of microscopic domain distribution into macroscopic behaviors. This model is able to calculate electric displacement, longitudinal, and transversal strains as a function of uniaxial electrical field. Good quality of the formulation is demonstrated through comparison with experimental data of the literature. In addition, results confirm our hypothesis of isochoric deformation of piezoceramics under electrical loading.

Domain motion modeling for hysteresis in piezoceramic materials under mechanical loading

The purpose of this study is to model domain motions of piezoceramic materials under mechanical loading to reproduce their hysteretic behaviors. Evolutions of remanent strain and remanent polarization are described by bridging the characteristics of microscopic domain distribution into macroscopic behaviors. Taking into account hysteretic behavior in unpoled piezoceramics, this model calculates electric displacement and longitudinal strain as a function of uniaxial mechanical field. Good quality of the formulation is demonstrated through comparison with experimental data. In addition, results confirm our choice of one single domain evolution law to describe domain motion in piezoceramics under mechanical and electrical loading.

Phase transition characterization based on acoustic reverberation time

Non-destructive monitoring of a material’s state during its physicochemical transformations is of interest for several industrial fields including food processing, such as milk-derived products, or cosmetics. The use of ultrasound to provide reliable information about physicochemical properties is becoming increasingly popular. Indeed, ultrasonic techniques have the main advantage of being rapid and non-invasive methods that allow parameters such as product composition, structure, and physical state to be obtained. Yet, classical techniques are limited to the characterization of the medium along the propagation path using the first wave packets. Here, we propose an alternative technique based on the study of the reverberated waves, classically used in room acoustics. In previous works, this method has shown its capability to characterize materials as well, with the advantage over classical techniques to address a medium in its whole structure. In this context, the determination of sol-gel phase transition...

Porous lead zirconate titanate ceramics with optimized acoustic properties for high-frequency ultrasonic transducer applications

Acoustic properties of porous PZT ceramics intended to be used as backing in high-frequency transducer applications are investigated using a novel method where an electroded piezoelectric thick film is deposited on the backing under test. Two backings with pore sizes 1.5 μm and 10 μm were obtained by sintering a mixture of ceramic powder and an organic template, their porosity was evaluated by scanning electron microscopy at 15%, leading to a density around 6.5 g/cm3. The electroacoustic impulse responses of these devices were measured considering the backing as a propagation medium, the initial thickness of which was chosen small enough to allow back-wall echoes to be detected and large enough to be able to separate the signals in time domain. Then the thickness of the backing was reduced (from around 2 mm to less than 1 mm) and the measurements were repeated. Acoustic properties were then deduced: attenuation coefficients reaching 4 dB/mm/MHz and group velocities around 3400 m/s were obtained, leading t...