Surface acoustics wave propagation characteristics on a langasite crystal plate

Propagation characteristics of a surface acoustic wave on a langasite (La3Ga5SiO14) crystal plate are studied mainly in terms of the temperature coefficients of resonant frequency (TCF). The coefficients are measured from the first resonant frequencies of one-port surface acoustics wave (SAW) resonators. It is clarified that a (90 degrees, 90 degrees, 175 degrees)-cut plate with the maximum theoretical coupling factor in the X-cut plate has a TCF of +25ppm/degrees C at 20 degrees C, a (90 degrees, 90 degrees, 25 degrees)-cut plate has a turnover point of 0 degrees C in the curve of relative resonant frequencies and a (90 degrees, 90 degrees, 15 degrees)-cut plate with the maximum theoretical power flow angle of 13.3 degrees in the X-cut plate has the minimum value of TCF in the wide temperature range of 50 degrees C to 100 degrees C. Experimental results suggest that the existence of the zero TCF substrate with k(2) of about 0.3% is expected.