All you need is an electronic frequency generator with several watts, driving a transformer to produce a high voltage AC (about 5000 Volts). In the vicinity of the natural resonance of the crystal one needs much less AC.

Dear Herbert

I need mechanical vibration without strong electrical field. How can I obtain mechanical vibration from a generator? 

Stacking several ceramic disks increases the mechanical amplitude and reduces the voltage needed down to several volts. Another possibility is to use a piezoelectric tube. Those elements are used in scanning tunneling microscopes.

Suitable piezoelectric transducers are used in security sirens and ultrasonic humidifiers.

Usually piezo transducers work at a resonance frequency, which is determined by the thickness and the weight attached to them.

For these purposes may be used magnetostrictive transducers, they allow large amplitude oscillations.

Hi Mehrdad,

It depends on orientation of vibration, are you looking for shear vibration or in-plane vibration?

Here we have shear transducers:

http://www.plantintegrity.com/

http://www.plantintegrity.com/contact/

Cheers,

Sina