A perturbation model to predict thermal sensitivity of transverse waves on thin quartz plates

The development of new acoustic wave devices has received increasing interest for various applications, particularly for sensors, but also in the telecommunication domain. The need to increase operating frequencies together with the efficiency of such devices pushes new principles to produce high-quality acoustic wave resonators and filters. Previous work has been done to experimentally measure the thermal sensitivity of transverse waves trapped by metal strip gratings deposited on thin quartz plates. Temperature compensation was found for AT-cut devices in an extended range of frequency, with the turnover temperature varying from 30 to 0 degrees C. Moreover, thermal compensation was found for higher-order modes in the Z cut, although the first mode exhibited a very high sensitivity to temperature. A theoretical model has been developed to explain these results. It is based on the Sinha-Tiersten perturbation approach combined with a model of unperturbed propagation, taking piezoelectricity into account. Comparison between the theoretical results provided by this model and experimental data is presented. A very good agreement is found for Z and AT-cut devices, even if second-order effects appear to be predominant in the latter case. (C) 1999 American Institute of Physics. [S0021-8979(99)06024-7].