Determination of full family of piezoelectric coefficients by measuring strain using vibrometer and fiber optic sensor

Date

2015

Authors

Vadlamani, Shri Ramya

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Abstract

PZT is the most widely used piezoelectric material when it comes to designing sensors and actuators. They are also well known for their applications in Micro Electrical Mechanical Systems (MEMS). It can be fabricated at low cost and hence is one of the most studied and widely used materials. It is necessary to study the piezoelectric coefficients of the materials accurately in order to design a sensor as an example, which defines their strain dependent applications. The piezoelectric coefficients can be determined, based on independent variables used, in two ways. The first method is to use the direct piezoelectric effect by applying force. Examples of these methods are normal loading method, Impulse method and wafer flexture method. The second method is to use the converse piezoelectric effect by applying electric field to the material. Examples of these methods are laser Doppler interferometry and atomic force microscopy, etc. The sample used for this study is PZT-4D, a commercial product of the modified PZT composition (Steminc, Miami, USA). This study examines the piezoelectric coefficients of the sample and compare with other methods. UHF-120 ultra-high frequency Vibrometer is used to measure the longitudinal piezoelectric displacement or x 33 and the MTI 2000 fotonic(TM) Sensor is used to measure the transverse piezoelectric displacement or x 31 . The frequency range analyzed is from 100Hz to 2MHz in both the methods. As the frequency ranges used by both the methods overlap it is easy to compare the results obtained by both the methods. A multiphysic Finite Element Analysis method, COMSOL, is also adopted in the study to generate three dimensional electromechanical coupled model based on experimentally determined strains x 33 and x31 as a function of frequency of the electric field applied. The full family of piezoelectric coefficients of the poled electronic ceramic PZT, d33, d31, and d15, can be then derived, upon satisfactory simulation of the COMSOL. This is achieved without the usual need of preparation of piezoelectric resonators of fundamental longitudinal, transversal, and shear modes respectively. In addition, directional dependence of each of the piezoelectric coefficients are analyzed using Mathematica to aid the optimized application of such piezoelectric ceramics.

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Keywords

PZT-4D, COMSOL

Citation

Department

Electrical and Computer Engineering