Sensitivities of surface acoustic wave sensors based on fine grain ceramics

The mass sensitivity for the Rayleigh surface wave of four piezoceramics, two modified lead titanates and two lead zirconate titanates is determined from the measurement of the phase shift of a SAW delay line when a thin aluminium film is vapoured on the surface. Mass sensitivities of 1.0/sup -3/ (Hz/MHz/sup 2/)/(ng/cm/sup 2/) at 25 MHz are found for the modified lead titanate ceramics and agree with theory. These results are discussed, and compared to the mass sensitivities of single crystals. They show that ceramics, which operate at lower frequencies, can compete with single crystals in gravimetric sensor applications.