Nowadays, piezoelectric materials are frequently used for various applications. They can operate under various environmental conditions, like high temperature, high pressure, external electrical DC fields or, residual or applied mechanical pre-stress (such as Tonpilz transducers). The presence of high mechanical or electrical pre-stress in piezoelectric materials induces modifications of their electroacoustic parameters.

For non hysteretic piezoelectric materials such as lithium niobate, the presence of a mechanical pre-stress induces a shift of their electroacoustic parameters through nonlinear modifications of their standard elastic, piezoelectric and dielectric parameters.

As far as hysteretic piezoelectric materials are concerned, such as piezoceramics, a pre-stress induces nonlinear hysteretic behaviours that significantly modify the piezoelectric characteristics through a shift of material properties from their pre-stress-free values. Nonlinear ferroelectricity may be characterized by four typical hysteretic loops: the dielectric (electric displacement versus electric field), the butterfly (strain versus electric field) and two ferroelastic curves (stress versus strain and stress versus electric displacement).

Thus, our work consists firstly in modelling the nonlinear effects of a mechanical pre-stress on both non-hysteretic and hysteretic piezoelectric materials. Secondly, our goal is to predict, quantify and compare with experimental values, the modifications of their electroacoustic parameters, such as coupling coefficient.

Below are few numerical and experimental results for two types of piezoelectric ceramics: PLZT and Barium Titanate, respectively.

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Recent associated publications:
R. Ul, F. Levassort, M. Lematre, L.-P. Tran-Huu-Hue, M. Pham-Thi, “Internal Electric Field in Co-Doped BaTiO3 With Co2+/3+, Nb5+, Li+, and F−: Impact on Functional Properties and Charge Compensation With Niobium and Fluorine Ions”, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, vol. 66, no. 1, pp. 154-162, 2019.

M. Lematre, R. Ul, L.-P. Tran-Huu-Hue, M. Lethiecq, “Electromechanical behavior of doped barium titanate piezoceramic under mechanical stress: modeling and comparison with experimental measurements”, IEEE Transactions on Ultrasonics, Ferroelectris and Frequency Control, vol. 67, no. 2, pp. 350-355, 2020.