High Power Piezoelectric Characterization System (HiPoCS™) | Chapter 5 | Physical Science: New Insights and Developments Vol. 2

 

Piezoelectric materials have been widely used in the automotive, medical instrument, information and telecommunication industry as sensors, actuators, frequency controlling devices, and high voltage and power sources. Piezoelectric devices make use of direct and inverse piezoelectric effects to perform a function. Both these piezoelectric effects are found in the crystal structures of some materials. 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 study describes the characterization methodologies of high-power piezoelectrics, in particular, in determining the three losses separately. ‘Intensive’ and ‘extensive’ losses are introduced in this study. Two broad categories of measurement techniques are discussed: (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 originates from the electromechanical coupling factor k2 loss, (𝑘2″𝑘⁢2′) = (2 tan 𝜃' - tan 𝛿' - tan 𝜙') Depending on the sign of the k2 loss, more efficient driving frequency can be derived rather than the conventional “resonance’ frequency. Recent studies on the loss determination methodology were also added in this study.

 

Author(s) Details

 

Kenji Uchino
International Center for Actuators and Transducers, The Pennsylvania State University, University Park, PA, USA.

 

Please see the book here:- https://doi.org/10.9734/bpi/psniad/v2/6033