High power piezoelectric characterization system (HiPoCS™)

Abstract

The bottleneck of the piezoelectric devices in miniaturization is the heat generation owing to the losses. There are three losses in a piezoelectric material; dielectric, elastic and piezoelectric losses. The development of high-power density piezoelectrics is directly relevant to the clarification of the loss mechanisms in such materials. This article describes the characterization methodologies of high-power piezoelectrics, in particular, in determining the three losses separately. There are two categories for the measuring methods: (1) electrical excitation method, and (2) mechanical excitation method. The former is basically admittance/impedance measurement via the output current over the input voltage, further classified into four methods; (a) constant voltage, (b) constant current, (c) constant vibration velocity, and (d) constant input energy. To the contrary, the latter is basically the transient mechanical vibration ring-down measurement under various electrical constraint conditions. The key is to obtain precise values of both mechanical quality factors at resonance QA and at antiresonance QB, regardless of measuring techniques, so that we can determine the piezoelectric loss precisely. The difference of QM between the resonance and antiresonance is originated from the electromechanical coupling factor k2 loss, Depending on the sign of the k2 loss, more efficient driving frequency can be derived rather than the conventional ‘resonance’ frequency.