Effective Electromechanical Coupling for the Partially Electroded Ceramic Resonators of Different Geometries
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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 keff = 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 keff = 0.67 for the electrode aspect ratio of 0.75. Partially electroded disc resonators (kpmode) are well described analytically by one-dimensional model only for the electrode aspect ratios up to 0.5. Maximum value keff = 0.58 for disc resonators was measured at the electrode aspect ratio equal to 0.80. Partially electroded ring resonators (kp-mode) show the same trend as discs without saturation of ECF values. Maximum ECF keff = 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.
- 2015 fascicula9 nr2