漏えいラム波用すだれ状トランスジューサの動作特性と漏えい表面波速度測定システム

抄録

The performance of an interdigital transducer (IDT) for leaky Lamb waves operating at a liquidsolid interface, and a system of measuring the distribution of leaky surface acoustic wave (SAW) velocity and attenuation are described. A leaky Lamb wave device with three arched-IDTs on one surface of a thin piezoelectric ceramic plate is introduced for the measuring system. A compressional wave reradiated into a water layer from the surface of a test sample is detected as electrical signals with different delay times at two receiving IDTs. The phase and amplitude difference between the two delayed signals are dependent on the leaky SAW velocity and attenuation on the test sample. It is essential for measuring leaky SAW propagation characteristics that the incident angle of the longitudinal wave propagating in the water layer is in the vicinity of the Rayleigh critical angle. The present method has the advantage of a wide measurable region of SAW velocity in comparison to the use of a conventional type of leaky SAW transducer because of plural dispersive leaky Lamb modes. In a typical case of using of NEPEC-6 produced by Tokin Corp. for a piezoelectric substrate, the measurable regions of using leaky SAW and Lamb wave transducers are around 2, 150 m/s and 2, 000_??_7, 000 m/s, respectively.