ABSTRACT An important characteristic of piezoelectric elements as energy converters is the energy conversion efficiency. The electromechanical coupling coefficient (EMCC) is commonly used as a measure of a piezoelectric elements' efficiency. The latest Standard on Piezoelectricity [1] recommends that EMCC be determined by the use of the Berlincourt et al. formula [2] for a uniform electroelastic state, and the dynamic formula by Mason [3] for near resonance frequencies. This paper is devoted to the analysis of these two formulas along with a third formula, which is discussed in [4]-[6]. The EMCC of commonly seen piezoelectric elements are formulated and analyzed. The comparison of the numerical results leads us to the following conclusions: 1.The formula of Berlincourt et al. is valid only for a uniform electroelastic state, 2. The dynamic formula of Mason gives the EMCC at a frequency equal to the arithmetic mean of resonance and the corresponding antiresonance frequencies, 3.The third formula for the EMCC is valid for both the static and dynamic electroelastic state of a piezoelement, and its results are in good agreement with those found by using Berlincourt's formula and the dynamic formula of Mason.
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