Material parameter determination of a piezoelectric disc with triple-ring-electrodes for increased sensitivity

A complete characterisation of piezo ceramic materials typically requires several differently processed specimen. Since the results of all these measurements are combined to form one single set of material parameters, inconsistencies occur naturally. The problem when considering only one specimen is the lack of sensitivity for several material parameters. Therefore, a triple-ring-electrode set-up is presented that is optimised to balance the sensitivity of the frequency dependent impedance for the full set of material parameters. This specific set-up is designed to characterise the material properties using only one specimen, hence reaching consistent material parameters while still aiming to be sufficiently sensitive to each parameter. This more complex set-up calls for a FEM-based inverse problem, that makes it possible to find parameters that fit the measured impedance. The whole optimisation procedure is described exemplarily for one specimen of PIC255 (PI ceramic, Lederhose, Germany) leading to feasible material parameters.