Doped PMN-PT Single Crystals

Requirements for high quality electrostrictive single crystals continue to be important because the polycrystalline PMN-PT materials, have a lower coupling coefficient . Single crystal PMN-PT doped with lanthanum or barium is an attractive transducer material because of its very high energy density and its capacity to undergo large electrostrictive strains. Foster-Miller has conceived of an innovative approach to grow uniformly doped large diameter PMT-PT single crystals either by itself or encapsulated in a porous single crystal sapphire skeleton. Our processing approach eliminates the following problems - small crystal size, high defect structure and cracking, associated with the current state of the art crystal growth processes. Additionally, our "sapphire/PMN-PT composite" will have a high fracture toughness and light weight without much reduction in the PMN-PT electrostrictive properties. Foster-Miller's process has the capability of growing single crystals at relatively low temperatures not possible with current crystal growth processes. Also, the nature of the isothermal process will promote uniform distribution of dopant species added during crystal growth. Our approach will be an enabling technology for producing low cost high efficiency, high strength electrostrictive single crystals. The process is versatile and has the potential to produce high quality piezoelectric and electrostrictive single crystal materials of other desired compositions. The Phase I program will involve growth of PMN-PT single crystal specimens and characterization including X-ray diffraction, dielectric and piezoelectric measurements. The Phase I team includes key researchers from Penn State University who are doing pioneering work in PMN-PT materials development under Navy funding. Foster Miller will provide five specimens to the Navy as deliverables.