New method of change in temperature coefficient delay of acoustic waves in thin piezoelectric plates

As is well-known, the development of highly effective and thermostable acoustic devices assumes using the acoustic waves with high coefficient of electromechanical coupling (K²) and low temperature coefficient of delay (TCD). At present, it also is well-known that fundamental shear horizontal (SH₀) acoustic waves in thin piezoelectric plates possess significantly more electromechanical coupling compared to surface acoustic waves (SAW) in the same material. However, although the value of TCD of SH₀ waves is insignificantly less than for SAW, this is not enough for development of thermostable devices. This paper suggests a new way of decreasing TCD of SH₀ waves in piezoelectric plates at a high level of electromechanical coupling. This way assumes to use the structure containing the piezoelectric plate and liquid with the special dependence of permittivity on temperature. Theoretical and experimental investigation showed that, for SH₀ wave in YX LiNbO₃ plate at hf=700 m/s (h=plate thickness, f=wave frequency) the presence of butyl acetate can decrease the value of TCD by six times at K²=30%. In a whole the obtained results open the wide prospect of using SH₀ wave in thin piezoelectric plate for development of highly effective and thermo-stable acoustic devices