Relaxor-PbTiO3 (PT) based ferroelectric crystals with the perovskite structure have been investigated over the last few decades due to their ultrahigh piezoelectric coefficients (d33 > 1500 pC/N) and electromechanical coupling factors (k33 > 90%), far outperforming state-of-the-art ferroelectric polycrystalline Pb(Zr,Ti)O3 ceramics, and are at the forefront of advanced electroacoustic applications. In this review, the performance merits of relaxor-PT crystals in various electroacoustic devices are presented from a piezoelectric material viewpoint. Opportunities come from not only the ultrahigh properties, specifically coupling and piezoelectric coefficients, but through novel vibration modes and crystallographic/domain engineering. Figure of merits (FOMs) of crystals with various compositions and phases were established for various applications, including medical ultrasonic transducers, underwater transducers, acoustic sensors and tweezers. For each device application, recent developments in relaxor-PT ferroelectric crystals were surveyed and compared with state-of-the-art polycrystalline piezoelectrics, with an emphasis on their strong anisotropic features and crystallographic uniqueness, including engineered domain - property relationships. This review starts with an introduction on electroacoustic transducers and the history of piezoelectric materials. The development of the high performance relaxor-PT single crystals, with a focus on their uniqueness in transducer applications, is then discussed. In the third part, various FOMs of piezoelectric materials for a wide range of ultrasound applications, including diagnostic ultrasound, therapeutic ultrasound, underwater acoustic and passive sensors, tactile sensors and acoustic tweezers, are evaluated to provide a thorough understanding of the materials’ behavior under operational conditions. Structure-property-performance relationships are then established. Finally, the impacts and challenges of relaxor-PT crystals are summarized to guide on-going and future research in the development of relaxor-PT crystals for the next generation electroacoustic transducers.

No abstract

No abstract

and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Departmentof Defense, Washington Headquarters Services, Directorate for Information . 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be award that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid 0MB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) 11-APR-2003 REPORT TYPEJournal article (refereed) NRL/JA/7430~03-4 DATES COVERED (From -To) TITLE AND SUBTITLE Role of Microbes in the SPONSORING/MONITORING AGENCY NAME{S) AND ADDRESS(ES)OFFICE OF NAVAL RESEARCH 800 NORTH QUINCY STREET ARLINGTON VA 22217-5660 SPONSOR/MONITOR'S ACRONYM(S) ONR SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release,distribution is unlimited Approved for public release, distribution is unlimited SUPPLEMENTARY NOTES Science Vol 303 6 February 2004 ABSTRACTTemperature, pressure, and tinne have been thought to control the smectite-to-lllite (S-1) reaction, an important diagenetic process used for petroleum exploration. We demonstrated that microorganisms can promote the S-1 reaction by dissolving smectite through reduction of structural Fe(lll) at room temperature and 1 atmosphere within 14 days. This reaction typically requires conditions of 300° to 350°C, 100 megapascals, and 4 to 5 months in the absence of micrcbial activity. These results challenge the conventional concept of the S-1 reaction and of reaction kinetic models. SUBJECT TERMS