A method of weak resonance for quality factor and coupling coefficient measurement in piezoelectrics

In the absolute-immittance spectrum of a piezoelectric resonator (PR), if the relative resonance-antiresonance frequency interval of a high-intensity resonance is basically determined by the coefficient of electromechanical coupling (CEMC), the relative resonance-antiresonance frequency interval of a low-intensity resonance with the resonance-antiresonance attenuation less than 15 dB, regardless of the reason, is determined by the quality factor Q of the resonance, and its intensity is proportional to the CEMC. The technique for the quality factor and CEMC determination based on the weak resonance (WR) concept has been formulated and then applied to low-Q and/or low-CEMC piezoelectrics, including the initial stage of piezoceramics polarization, and to piezotransducers under electrical or mechanical loading with maximum efficiency. The WR method allows one to determine the quality factor on PRs under specific conditions, such as arbitrary PR shape resulting to a broken frequency spectrum; PRs with an extremely large or extremely low electrical capacitance; at high-order PR harmonics; electrodeless piezoelements under mechanically contactless electrical excitation; determining the local thickness-mode material quality factor value and its distribution along the surface of a thin electrodeless piezoplate-all this where the traditional methods show a poor performance or do not work at all.