New Material Compositions that Expand the Operating Domain of Piezoelectric Single Crystals

At the present time, large-sized PMN-PT piezoelectric crystals, 3" diameter by 8" long, of high quality, can be grown directly from the melt and are commercially available. The objective of this proposal is to demonstrate the feasibility of expanding the operating domain of the PMN-PT based piezoelectric crystals by chemical doping and compositional refinements. Although the piezoelectric properties of PMN-PT crystal products are qualified to the military, and are commercially used in medical ultrasound imaging (and a variety of acoustic transducers), the coercive electric-field strengths and thermal stability need to be improved particularly for large signal/high energy applications. This is very important for Navy sonar transducers. For acoustic sensors, such as hydrophones and vector accelerometers, that require high signal/noise ratios, lowering of the dissipation factor is a key parameter while maintaining the giant-piezoelectric response characteristics. Radiation with high energy particles (e.g., neutrons) can localize "defects" that pin domain wall mobility. It expected that selected radiation damage will enhance coercivity. It is well known that the PMN-PT solid-solution system is the only one that is near congruent solidification, thus enabling the direct growth from the stoichiometric melt in a most cost-effective manner. This proposal focuses on new compositions that must be near congruent melting. Thus, the proposed work for new compositional refinement to PMN-PT based crystals will be of immediate applicability to the growth of large crystals, thus expanding the operating domain of piezoelectric single crystals.BENEFITS: The proposed work will enhance the piezoelectric performance of PMN-PT based crystals by chemical doping and compositional refinement using our proprietary and cost-effective Bridgman growth method. The proposed work is targeted for high-drive applications for single crystals in Navy sonar, torpedo guidance, torpedo counter measures, sensors, vibration control, shape control, position control, and also for commercial applications such as medical ultrasound imaging, nondestructive testing, etc. We anticipate domain-engineering will increase the properties of the final transduction devices.