A measurement system of SAW velocity distribution using a layer-structure transducer for a leaky SAW

An ultrasonic system in which a leaky surface acoustic wave (SAW) transducer is composed of a piezoelectric ceramic thin plate, an interdigital transducer (IDT), and a fused quartz plate for measuring the distribution of leaky SAW velocity on a test sample is described. A compression wave reradiated into a water layer from the surface of the test sample is detected as electrical signals with different delay times at receiving IDTs. The phase difference between the two delayed signals is dependent on the leaky SAW velocity on the test sample. This method, which uses a layer-structure leaky SAW transducer, has the advantage of a wide measurable region of SAW velocity, unlike the normal kind of leaky SAW transducer, because of plural dispersive leaky SAW modes. Experimental results for a LiNbO₃ wafer and a glass substrate were obtained using three dispersive leaky modes