Surface Wave Delay Lines with Interdigital Transducers on Unpolarized PZT Ceramic Plates

Abstract

Characteristics of surface wave delay lines with interdigital transducers on unpolarized PZT ceramic plates are studied. The slower sound velocity in an unpolarized PZT plate insures a longer delay time compared to that of the prepolarized plate with the same dimension. The polarizing treatment is given only to the parts of the specimen under the electrodes to convert them into transducers by a DC electric field of 1,500 V/mm at 80°C for 10 to 20 hours and a subsequent aging at 120° for 10 to 20 hours. This polarizing treatment makes it possible to excite a surface wave of a shorter wavelength compared with those excited in a uniformly polarized sample. Thus a higher center frequency of the delay line can be obtained. Preliminary results on the attenuation constant of surface waves in the delay lines are presented.