Effective Electromechanical Coupling for the Partially Electroded Ceramic Resonators of Different Geometries

Jiří Erhart; Tutu Sebastian

Jiří Erhart Technical University of Liberec
Tutu Sebastian Technical University of Liberec

Keywords: piezoelectric ceramics, PZT, resonator, vibration modes, electromechanical coupling factor

Abstract

Effective electromechanical coupling factor (ECF) was studied on bar, disc and ring ceramic resonators partially covered by electrodes. ECFs were calculated theoretically and verified experimentally. Bar resonators (k₃₁-mode) show maximum value of ECF k_eff = 0.26 at the electrode aspect ratio equal to 0.75 with calculated values fitting the experimental data for all aspect ratios. Calculations for bar resonators with embedded electrodes (k₃₃-mode) show similar behavior like for k₃₁-mode, but at higher ECFs. Maximum value of ECF for such a mode reaches k_eff = 0.67 for the electrode aspect ratio of 0.75. Partially electroded disc resonators (k_p-mode) are well described analytically by one-dimensional model only for the electrode aspect ratios up to 0.5. Maximum value k_eff = 0.58 for disc resonators was measured at the electrode aspect ratio equal to 0.80. Partially electroded ring resonators (k_p-mode) show the same trend as discs without saturation of ECF
values. Maximum ECF k_eff = 0.34 was measured for ring resonators with full electrode. The presented analytical formulae may serve as a guide for the optimum electrode pattern design for the partially electroded resonators.

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