N101-092 TITLE: Cost-Effective PiezoCrystal Transducer Assembly Technologies

TECHNOLOGY AREAS: Materials/Processes, Sensors

ACQUISITION PROGRAM: PMS 415 Undersea Defensive Warfare Systems: Next Generation Countermeasure

OBJECTIVE: Devise and demonstrate innovative materials processing methods for the cost-effective fabrication of relaxor piezoelectric single crystals into complex SONAR transducer assemblies. Candidate technologies in the fabrication of PiezoCrystal transducers include, but are not limited to: forming the as-grown crystalline material into the desired shapes, electroding the crystal, attaching electrical leads, poling the crystal, bonding crystal to crystal, bonding crystal to metals, bonding crystal to insulators, and bonding crystal to polymers.

DESCRIPTION: More than a decade ago a class of materials (relaxor piezoelectric single crystals) came to the fore whose electromechanical transduction properties greatly exceeded those of legacy materials (primarily, piezoelectric ceramics): electromechanical coupling greater than 90% (versus 70-75%) and strain levels greater than 1% (versus, less than 0.1%) [References 1 and 2]. Based on these materials acoustic transducers have been demonstrated with dramatically enhanced performance over what is achievable with the legacy technology --- for example, increased bandwidth (>x2), source level (+12 dB), sensitivity (+12 dB), compactness (>x3) and lightness (>x2) [Reference 3]. These device performance gains (totaling one to two orders of magnitude) have yielded gains, at the system level, of factors of two to six [Reference 4]. Indeed, the PiezoCrystal transducer technology makes possible some systems that simply would not be practical with the legacy technology. Navy SONAR systems have already completed the technology development and demonstration phase and are poised to enter the system development and demonstration as part of the acquisition process. To date, these PiezoCrystal devices have been fabricated by adapting, at the gallop, legacy transducer fabrication methods. This topic aims to devise and validate innovative assembly fabrication methods specifically tailored for the relaxor piezoelectric single crystals.

PHASE I: Select one or two candidate fabrication technologies and devise innovative methods specifically for relaxor piezoelectric single crystals. Demonstrate the efficacy of the new methods by building and testing a candidate SONAR transducer. It would be a big plus if the candidate transducer demonstrated was for a real Navy SONAR system.

PHASE II: Develop a full spectrum of piezocrystal transducer fabrication technologies and demonstrate their efficacy by building and testing one or more piezocrystal transducers for insertion into a SONAR system in development or for upgrading a SONAR system already in production.

PHASE III: The technologies developed by this research will be used to fabricate development and production piezocrystal transducers for a broad spectrum of Navy SONAR systems: countermeasures, mine hunting, torpedoes, acoustic modems, towed arrays, moored arrays, sonobuoys, and the like.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The technology developed for defense transducers will be immediately applicable to transducers in civilian SONAR systems. Moreover, these assembly fabrication technologies will be readily transferred to making electromechanical sensors and actuators for a broad spectrum of civilian applications ranging from hydraulic servo valves, through vibration energy harvesters, to robotic manipulators.

REFERENCES:
1. S.E. Park and T.R. Shrout, "Ultrahigh Strain and Piezoelectric Behavior in Relaxor based Ferroelectric Single Crystals, " J. Appl. Phys., 82[4], 1804-1881 (1997).

2. S.E. Park and T.R. Shrout, "Characteristics of Relaxor-Based Piezoelectric Single Crystals for Ultrasonic Transducers," IEEE Trans. On Ultrasonic Ferroelectrics and Frequency Control, Vol. 44, No. 5, 1140-1147 (1997).

3. J. M. Powers, M. B. Moffett, and F. Nussbaum, "Single Crystal Naval Transducer Development," Proceedings of the IEEE International Symposium on the Applications of Ferroelectrics, 351-354 (2000).

4. T. C. Montgomery, R. J. Meyer, and E. M. Bienert, "Broadband Transduction Implementation and System Impact," Oceans 2007, 1-5 (2007).

KEYWORDS: piezoelectric single crystals; SONAR transducers; fabrication technologies; electroding; bonding; poling

** TOPIC AUTHOR (TPOC) **

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