Effective Piezoelectric Constant Research Articles

Piezoelectric tubes and tubular composites for actuator and sensor applications

Piezoelectric actuators and sensors made with a tubular structure can provide a great agility of effective response in the radial direction. For a radially poled piezoelectric tube, the effective piezoelectric constant in that direction can be tuned to be positive, zero or negative by varying the ratio of the outer radius (Ro) to the inner radius (ro) of the tube. For a suitable ratio of Ro/ro, this effective constant can also be changed in sign or set to zero by adjusting the d.c. bias field level for tubes made of electrostrictive materials. Therefore, one can make a piezoelectric transducer with all the effective piezoelectric tensile constants having the same sign. End-capped thin-walled tubes also exhibit an exceptionally high hydrostatic response, and the small size of the tubular structure makes it very suitable for integration into a 1–3 composite which possesses low acoustic impedance and high hydrostatic response.

An analysis of surface acoustic wave propagation in a piezoelectric film over a GaAs/AlGaAs heterostructure

This paper presents a theoretical analysis of the surface acoustic wave (SAW) propagation in a GaAs/AlGaAs heterostructure covered with a piezoelectric film such as ZnO, BaTiO3, PbTiO3 or PZT. We calculate the SAW potential profile, SAW velocity, and effective piezoelectric coupling constant as functions of the film thickness using a Laguerre polynomial technique. The effective material constants such as the characteristic admittance and equivalent dielectric constant are also obtained. We concentrate on the suitable choice of the film for a heterojunction acoustic charge transport device. A ZnO film of 0.3–0.5 acoustic wavelength thickness seems to be the most suitable choice.

Electromechanical coupling of surface acoustic waves in the vicinity of the phase transition in triglycine sulfate

The temperature dependences of an effective piezoelectric constant have been determined in the vicinity of the Curie temperature in the presence of externally applied electric fields from simultaneous measurements of the temperature variations of the electromechanical coupling constant of surface acoustic waves and of the dielectric constant. It is shown that the experimental results can be explained on the assumption that piezoelectricity in triglycine sulfate is of an ’’induced’’ and not an ’’intrinsic’’ nature.