Resource for Piezoelectric Single Crystals

Abstract

Abstract : This report documents work performed over the period of April 1, 1998-July 1, 2001 under the ONR/DARPA program titled 'Resource for Piezoelectric Single Crystals', contract no. N00014-98-1-0527. The program encompasses novel piezoelectric materials, characterization, and domain studies, innovative growth technique and device engineering, the latter including MEMS and electro-optics. Research on this program is represented in the technical appendices. The program was on domain/crystallographic engineering of Relaxor-PT single crystals, e.g., Pb(Zn(1/3)Nb(2/3))O3-PbTiO3 and Pb(Mg(1/3)Nb(2/3))O3-PbTiO3. From this program, it was confirmed that in single crystal form, Relaxor-PT materials offer significant piezoelectric performance with coupling coefficients greater than 90% and strains exceeding 1%. In Characterization, the complete set of dielectric, piezoelectric, and elastic coefficients were determined for domain engineering rhombohedral PZN-4.5%PT, PZN-8%PT, and PMN-33%PT crystals. For all the systems characterized, coupling coefficients (k33 > 90%) with piezoelectric strain coefficients (d33 > 2000 pC/N) were found. The concept of cryogenic poling was utilized to reduce property variation among crystals relatively close to the morphotropic phase boundary, due to rhombohedral-tetragonal transformations. Domain studies revealed the complexity of the crystals in terms of the macrosymmetry being orthorhombic mm2 or lower than the assumed 4mm. The possibility of a monoclinic phase was suggested to aid in the understanding of the complex domain configuration of underlying high piezoelectric activity. In addition to high temperature flux and Bridgman growth technique, Laser Heating Pedestal Growth crystal of non-lead Zr modified BaTiO3 and PMN-PT were successfully grown with rates > 0.3 mm/min. The concept of domain engineering was demonstrated on non-PbO ferroelectrics with enhanced levels of piezoelectric activity confirmed.