Piezoelectric Ceramic Reproducibility (For 33 Mode Transducer Applications)

Abstract

The lack of reproducibility and uniformity of piezoelectric ceramics is a problem that has plagued the Navy for over 30 years. As a result, and the need to specify ceramic for competitive procurements, the Navy has developed specifications that accommodate the variability of the ceramic and assure the transducer will meet performance requirements, be electroacoustically interchangeable, and be intermixable with existing units. A Simplified Guidance Xodel ( S G M ) has been developed that provides insight into the relationship between ceramic parameters and transducer design and performance. Experimental data are presented that validate the SGPl. New methods are presented to extract the piezoelectric material parameters from geometry dependent 33 mode ceramic rings. A dynamic tester has been developed to certify the performance of a composite ceramic stack. applications. Figure 1 shows a cut-away of a typical transducer element of interest. To achieve the solution, complicated computerized predictive models had to be augmented by what has been called a Simplified Guidance Model ( S G M ) in order to deduce the kernel of the solution. The heart or kernel of the solution has been referred to as DAS-7. It is a design adjustment method that allows one to match the electroacoustic performance of a proposed transducer to that of a baseline, and assure that the new transducer will duplicate the baseline and be electroacoustically interchangeable and intermixable. A derivation and discussion of the SGM and the relationship of the parameters in DAS-7 is presented in reference [ I ] . Simply stated, DAS-7 requires the rnanuEacturer to match the piezoelectric constant, d33, and free capacitance, CT, of the ceramic, t o that of the baseline. If, however, the manufacturer is unable to match both quantities, then he shall match the d33. The lack of reproducibility and uniformity of piezoelectric ceramics is a problem that has plagued the Navy since the introduction of ceramic sensors into fleet transducers over 30 years azo. After the d33 match has been achieved, then a As a result of this situation and the need to be one-time area adjustment, within prescribed limits, able to specify the piezoelectric ceramic €or a is allowed to either increase o r decrease CT to build-to-print Fabrication Specification Package match the baseline. Once the d,,, and CT, match ( F S P ) , a solution to the problem was developed. The Sonar Transducer Reliability Improvement Program (STRIP), with some assistance from the Transduction Sciences Program, has developed a complete, practical solution to the problem of reproducibility for a certain class of 33 mode transducer <_I has been achieved, the final criterion is that the compliance of the ceramic be such that when a stack is fabricated and placed in a primary subassembly, there must exist an acceptable fiberglass tuning ring to tune the assembly to the required resonznce frequency. Cut-away of Typical 33 Xode Transducer