Pure-Mode Loci in Piezoelectric Plate Resonators: Application to Materials Evaluation in Class 4mm

The accuracy of piezoelectric materials evaluations can be enhanced by the use of pure-mode orientations, provided that exact analytic expressions for the pure-mode eigenvalues are known. The accuracy is enhanced by eliminating the need to extract constants from the differences in sums and products of measured quantities. Previous studies of pure-mode loci have not addressed the need for an engineering methodology for pure-mode sample set selection for materials evaluation. In light of this, it has been found necessary to adopt an alternate approach for determining the pure-mode loci in piezoelectric crystals. The alternate approach yields simple analytic expressions for the stiffness eigenvalues and provides a convenient engineering methodology for pure-mode sample set selection. The paper reviews the theory of simple thickness modes in piezoelectric plate vibrators, the alternate approach to the determination of pure-mode loci and its application to pure-mode sample set selection for dilithium tetraborate is presented, and thickness- and lateralfield excitation considerations are discussed.