HIGH-FREQUENCY, HIGH-TEMPERATURE ULTRASONIC TRANSDUCERS

Piezoelectric films of 100% (002) oriented AIN were deposited on platinum-coated quartz, sapphire and LMN ceramics via a CVD process. The growth rate achieved was > 20 nm s-1 at 1020-1040 K. These films had the highest figure of merit (125) and dielectric strength ( > 2 x 10(7) V cm-1) of any known piezoelectric material. The relative dielectric constant is approximately 8.6 and the thickness coupling coefficient, k(t), 20%. The films exhibit ultrasonic response for temperatures less-than-or-equal-to 1430 K. 30 MHz compressional-wave transducers were developed on quartz delay-rods with signal strength comparable to ZnO devices. Non-cooled, high temperature ultrasonic devices were developed using the oriented AIN films.