Regarding the determination of the electromechanical coupling factor of a ferroelectric plate vibrating in thickness-shear mode

This paper deals with the determination of the electromechanical coupling factor k₂₆ of selected rotated Y-cut quartz homeotype gallium orthophosphate (GaPO₄) resonators, and k₁₅ of a polarized ferroelectric PZT plate, vibrating in the thickness-shear mode. The IRE standards on piezoelectric crystals recommends the application of the dielectric method and determination of the thickness-shear coupling factor from the measurement of the free and clamped permittivities of the sample. In this case, it is not easy to define the frequency at which the clamped permittivity has to be measured, ft is known that the electromechanical coupling factor is also useful to express the influence of piezoelectric properties on the resonance frequency of the plate thickness shear vibrations. We used this knowledge to propose a resonance method for the determination of the electromechanical coupling factor k₂₆ of rotated Y-cut GaPO₄ resonators, and k₁₅ of a polarized ferroelectric PZT plate. The modified method is described in this contribution and the results of the measurements of k₂₆ and k₁₅ with the modified resonance method are discussed.