Cost-Effective Fabrication of Piezoelectric Single Crystals Device Elements

For the proposed work, TRS Technologies, Inc., in collaboration with The Penn State Electro-optics Center (EOC), and Dr. David J. Quesnel at the University of Rochester will investigate increasing the yield of damage minimized or damage free piezoelectric single crystals by establishing an optimal parameter matrix for PMN-PT crystal machining involved in wafer and element processing (slicing, lapping, polishing, dicing, and drilling) and then evaluate the merit of these techniques. The surface finish and subsurface damage will be analyzed to determine the optimal slicing techniques and lapping/polishing/chemical etching procedures. A matching layer technique will be developed to significantly reduce edge chipping and micro cracking, which are the main issues in current dicing and drilling processes. Since PMN-PT wafer fabrication is the first step in device manufacture, wafer inspection will be very important for quality control purposes. As part of the Phase I program, residual stress and machining-related defects will be studied with photoelastic stress imaging, to establish the feasibility of PMN-PT wafer inspection by this technique in a mass production environment. At the end of Phase I program, a high yield, cost-effective methodology for PMN-PT crystal wafer and component fabrication will be identified and the cost-effectiveness of different manufacturing approaches will be compared. BENEFITS: TRS’ strategy in commercializing single crystal piezoelectrics has been to use government funded R&D programs to develop pilot manufacturing processes capable of supplying crystals to concurrent transducer development efforts. TRS sees medical ultrasound as the primary commercial market for single crystal piezoelectrics outside of the DOD. However, acceptance has been slow, because of high crystal cost and poor uniformity. If the objectives are met on this program and optimized in Phase II, it will greatly enhance the supply of high quality PMN-PT single crystal based components. This will in turn help to the commercialization efforts of the companies and organizations that are developing next generation applications based on this material. Coupled with development of the Bridgman growth of PMN-PT, with refinements such as zone melting, an optimized manufacturing process will yield high quality crystals with size and uniformity sufficient for Navy Sonar applications and medical ultrasound markets. Thus, upon successful completion of the Phase II program TRS plans to market, high quality, compositionally uniform, defect free or defect minimized PMN-PT to these markets. Once an ultrasound company or defense contractor decides to begin commercialization of crystal based devices, TRS will seek to scale-up manufacturing production. TRS will most likely see investment for this scale-up from the ultrasound companies themselves and/or private investors. We have successfully used private investment in the past to transition government funded R&D to commercial products.