Characterization of Piezoelectric Materials for Transducers Stewart Sherrit Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA, [email protected] Binu K. Mukherjee Physics Department, Royal Military College of Canada, Kingston, ON, Canada, K7K 7B4. [email protected] 1.1 Introduction Implementing piezoelectric materials as actuators, vibrators, resonators, and transducers requires the availability of a properties database and scaling laws to allow the actuator or transducer designer to determine the response under operational conditions. A metric for the comparison of the material properties with other piezoelectric materials and devices is complicated by the fact that these materi- als display a variety of nonlinearities and other dependencies that obscure the direct comparisons needed to support users in implementing these materials. In selecting characterization techniques it is instructive to look at how the material will be used and what conditions it will be subjected to. However in order to define metrics for the higher order effects we need to first quantify the ideal lin- ear behavior of these materials to generate a baseline for the comparisons. A phenomenological model derived from thermodynamic potentials mathematically describes the property of piezoelectricity. The derivations are not unique and the set of equations describing the piezoelectric effect depends on the choice of potential and the independent variables used. An excel- lent discussion of these derivations is found in (Mason 1958). In the case of a sample under isother- mal and adiabatic conditions and ignoring higher order effects, the elastic Gibbs function may be de- scribed by ( ) 1 1 2 2 D ijkl ij kl nij n ij mn m n G s TT g DT D =− + + β 1 2 T D , (0.1) where g is the piezoelectric voltage coefficient, s is the elastic compliance, and β is the inverse per- mittivity. The independent variables in this equation are the stress T and the electric displacement D. The superscripts of the constants designate the independent variable that is held constant when defin- ing the constant, and the subscripts define tensors that take into account the anisotropic nature of the material. The linear equations of piezoelectricity for this potential are determined from the derivative of G 1 and are 1 1 , D ij ijkl kl nij n ij T m mn n m G S s T g T G nij ij D E D g T D ∂ =− = + ∂ ∂ = =β − ∂ (0.2) where S is the strain and E is the electric field. The above equations are usually simplified to a re- duced form by noting that there is a redundancy in the strain and stress variables (Nye 2003) or (Cady 1964) for a discussion detailing tensor properties of materials). The elements of the tensor are con- tracted to a 6 × 6 matrix with 1, 2, 3 designating the normal stress and strain and 4, 5, and 6 designat- ing the shear stress and strain elements. Other representations of the linear equations of piezoelectric- ity derived from the other possible thermodynamic potentials are shown below (Ikeda 1990, Mason 1958). These sets of equations (0.3)-(0.6) includes equation (0.2) in contracted notation. 1
Characterization of Piezoelectric Materials for Transducers
Jun 26, 2023
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Related Documents
