Contribution to the electromechanical and nonlinear properties of GaPO4 crystals

In the last decade a strong, attention is given to the piezoelectric crystals with a large value of the electromechanical coupling coefficient. Namely quartz homeotypes crystals as a berlinit, langasit and also gallium ortophosphate (GaPO4) are the representatives of this group of crystals. Approximately two times greater coupling coefficient k(26) connected with the resonators vibrating in the thickness-shear mode allows extend the distance between the series and parallel resonance frequency of the resonators suitable for the frequency range from 1 to 100 MHz. This is important for some types of crystal oscillators and wave respectively monolithic filters. The large electromechanical coupling coefficient increases also the difference of the resonant frequency temperature dependence of the fundamental and harmonic resonance frequencies of the resonators vibrating in the thickness-shear mode. The results of the measured resonance frequency temperature characteristics of fundamental and thrice harmonic of Y-cuts of GaPO4 resonators vibrated in thickness-shear mode are presented. The computed electromechanical coupling coefficient k(26) are compared with the measured ones. A great attention is further given to the measurement of some nonlinear properties of the rotated Y-cuts GaPO4 resonators vibrating in essentially thickness-shear mode. The knowledge of the nonlinear interactions is important for the analysis of intermodulation phenomena resonators. This phenomena is important for the application of the GaPO4 resonators in crystal oscillators, filters and other electronic devices,