Superhigh electromechanical coupling for acoustic plate waves in potassium niobate

The characteristics of acoustic waves propagating in thin plates of single crystal potassium niobate are theoretically investigated. It is found that acoustic plate waves can provide extremely high values of electromechanical coupling. For example, values of Delta v/v, the fractional velocity change produced by electrical shorting of the surface, as high as 0.5 can be obtained with the shear horizontal (SH0) wave. The influence of a thin conducting layer on the velocity and attenuation of plate waves is investigated. It is shown that variations in these parameters as high as 50% and 30 dB per wavelength can be achieved for change in layer sheet conductance from 10(-7) to 10(-5) S.