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 × 10⁷ V cm^?1) of any known piezoelectric material. The relative dielectric constant is 8.6 and the thickness coupling coefficient, K_t, 20%. The films exhibit ultrasonic response for temperatures 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.