Dickenschwingungen kreisförmiger Scheiben aus Bariumtitanatkeramik

1. The frequency of minimum electrical impedance of a piezoelectric barium titanate cylindrical disk differs less than 1% from the resonance frequency of the pure thickness mode of an infinite plate, if the diameter to thickness ratio 2 a/d exceeds 23. The uncertainty of the electromechanical coupling coefficient determined by the resonance and anti-resonance frequencies amounts up to 10%. The fluctuations of the radial amplitude pattern are considerable. But there occur hardly any nodal circles.

2. For the third harmonic similar results have been obtained for relatively thick disks (5,5 < 2 a/d < 6).

3. Isolation of one mode and flattening of its amplitude pattern is possible by facetting the disk (grinding the edges).

4. Mounting of the disks by clamping them between lead rings as is often done in ultrasonic transmitters changes the vibration pattern and causes additional damping.

5. With increasing excitation voltage the mechanical quality factor decreases without an essential change in the vibration pattern.