Leakage electric field in longitudinal vibration from piezoelectric bars

Abstract

The edge effects due to leakage electric fields in piezoelectric bar specimens cause non-uniform charge densities, distort electric field lines, and increase capacitance. This increase in capacitance was simulated using finite-element-method-based electric field simulation software. The two-dimensional and three-dimensional simulation results showed that the rate of increase in capacitance decreased when the aspect ratio or dielectric constant increased. To increase measurement accuracy of the dielectric, piezoelectric, and elastic constants of piezoelectric single crystals, the rate of increase in capacitance should be maintained below 0.5%. Actual measurements and theoretical analysis of the transverse- and longitudinal-effect length-extensional vibration in specimens with a small dielectric permittivity were performed. The results indicated that can be obtained directly from the fr of a transverse-effect length-extensional vibration, but kij and dij must be compensated for if the rate of increase in capacitance is greater than 0.5%. After compensation, it is possible to measure kii from longitudinal-effect length-extensional vibration in specimens with a reasonable dielectric permittivity, but one must avoid using it to measure and