Papers by Keyword: Electromechanical Coupling Coefficient

Abstract: We had investigated the electromechanical coupling coefficient (K²) of surface acoustic wave (SAW) on proton-exchanged (PE) and annealed PE (APE) z-cut LiNbO₃ waveguides using octanoic acid. The penetration depth of hydrogen assumed to be equal to the waveguide depth (d) was measured by secondary-ion mass spectrometry (SIMS). The frequency response of SAW was measured with a network analyzer. The annealing process was carried out in a horizontal furnace kept at 400°C for 2 h under a dry O₂ gas flow. The change of K² in PE and APE samples fabricated under different conditions was dependent on kd, where k was the wavenumber. The experimental results showed that the variation of K² in PE samples was significantly decreased with the increase of kd. The reduction of K² may be due to the reduced piezoelectric coefficients in the PE layer. On the other hand, the variation of K² in APE samples also exhibited the decreased tendency after annealing. It indicated that the annealing process could not restore the reduction of K² caused by the PE process.

Abstract: Legendre polynomial method which describes the structure and incorporates automatically the boundary conditions in constitutive and propagation equations is used to model acoustic wave cylindrical resonators. It is the first time this method is applied to study standing rather than propagative waves. The advantage of this approach is, in a unique formulation, to take into account electric sources. The analytical and numerical resolutions are presented to highlight the potentialities of the Legendre polynomial approach. The vibration characteristics of piezoelectric discs with regard to diameter to thickness D/H ratios are analyzed by the three dimensional modeling approach through both modal and harmonic analyses. Resonance and antiresonance frequencies, electric input impedance, dispersion curves, field profiles and electromechanical coupling coefficient, easily obtained, are presented for PZT5A resonator piezoelectric discs. To validate our approach, the results using our 3D polynomial modelling of acoustic wave resonator are compared with those obtained by an approximated analytical method. The developed software proves to be very efficient to retrieve the radial modes of all orders.

Abstract: The electromechanical properties of cymbal piezocomposite transducer were investigated in this paper. Piezoelectric ceramic PZT—5A was used as piezoelectric phase of transducer, and brass foil was used as end cap electrode of cymbal piezocomposite transducer. Several types of this transducer were fabricated. The displacements of this transducer as functions of the applied force and the applied electric field were investigated. It was calculated and analyzed for the energy transmission coefficient and electromechanical coupling coefficient of this transducer which optimum values were obtained.