"NOVEL ACOUSTICS TRANSDUCERS"

Inventors: R.E. Newnham, et al.

PSU Inv. Disc. No. 959

Issued U.S. Patent No. 4,999,819

The inventors have developed a new type of piezoelectric ceramic-metal composite based on the principle of flextensional transducer. To enhance dh, the transducer converts a portion of the z-direction stress into large radial and tangental stresses of opposites signs, thereby causing the d33, d31 and d32 contributions to dh to add rather than subtract, leading to high dh. The structure is designed to obtain an extensional vibration mode of ferroelectric ceramics, and high hydrostatic pressure tolerance. If necessary, the large compressive prestresses can be applied to reduce aging effects in the piezoelectric ceramic. The metal sections protect the shallow cavities at the interfaces and allow the transducer to withstand high external stresses and shock waves. The transducer's design eliminates bending stresses which otherwise fracture the ceramic. Design flexibility allows to produce transducers for the use in the necessary temperature range.

In summary, this invention represents a compact, highly reliable transducer with an extremely large figure of merit capable of functioning in hostile environments. This transducer has potential applications in medical, sonar, non-destructive testing and other fields. Specific products that could possibly be developed are petroleum exploration detectors, fish finders, optical scanner units, ink jet printers, ultrasonic glasses for the blind, fetus heart monitoring devices and ultrasonic speedometers.