On complications associated with measuring the piezoelectric properties of relaxor single crystals with high electromechanical coupling using resonant bar samples and comparison with a lumped parameter method.

The development of relaxor single crystal piezoelectric materials with exceptionally high electromechanical coupling (k above 0.85) and high elastic and piezoelectric anisotropy presents challenges and questions to the applicability of the use of traditional resonant bar methods (IEEE Standard on Piezoelectricity, 176-1987, Sec. 6.4) for determining the constituent piezoelectric properties. Standard bar techniques for determining coupling coefficient rely on the single degree of freedom electromechanical circuit models for sufficiently long samples whereby measurements of isolated resonances and antiresonance frequencies are uncorrupted by lateral resonances. The limited applicability of the standard method for these piezoelectrics has motivated the development of an alternative method that avoids many of the previous short comings. A lumped parameter dumb-bell resonator approach was implemented by employing a small single crystal piezoelectric sample sandwiched between reactive terminations whereby the piezoelectric and elastic properties may be determined. Coupling coefficients k-33 and k-31 as high as 0.88 were measured for single crystal CPSC160-95 and CPSC180-120 by Ceracomp.