Aspect ratio dependence of d15 measurements in Motorola 3203 material

The measurement of piezoelectric coefficients is a subject that has received considerable attention, with the exception of shear mode excitation. The aspect ratios necessary to provide accurate, reproducible measurements of d15 in Motorola 3203 are explored using impedance spectroscopy. It is shown that a minimum aspect ratio of 20:1 is necessary in the dimensions of the ceramic between the field and the polarisation directions (lt) to provide reproducible measurements, contrary to previous work. A width contribution to the measurement results is highlighted leading to a minimum aspect ratio of 6:1 between the width and the thickness (w/t). It is suggested that the width contribution is a result of a distribution of dipole vectors around the poled direction.