Electrically excitable purely mechanical resonances in piezoelectric and ferroelectric materials - geometrical considerations

Mechanical displacements of electrically excited specimens of piezoelectric and ferroelectric materials are determined using a displacement laser interferometer system. It is found that purely mechanical resonances can exist in these specimens independent of any detectable electrical disturbance, including virgin and depoled specimens of ferroelectric ceramics. For specimens of the ceramic PZT8 it is shown that the number of purely mechanical resonances increases with decreasing specimen thicknesses, but there seems to be no other correlation between the resonances and the geometries of the specimens. Preliminary experimental evidence indicates that for the case of ferroelectric ceramics occurrence of the resonances may be due to the coupling of the driving voltage to the unit cell dipoles of the domains - this is suggestive of a dependence of domain structure.