【正文】 ION OF PIEZOELECTRIC CERAMlClPOLYMER COMPOSITES BY INJECTION MOLDING.Leslie J. Bowen and Kenneth W. French,Materials Systems Inc.53 Hillcrest Road, Concord, MA 01742AbstractResearch at the Materials Research Laboratory, Pennsylvania State University has demonstrated the potential for improving hydrophone performance using piezoelectric ceramic/polymer posites. As part of an ONRfunded initiative to develop costeffective manufacturing technology for these posites, Materials Systems is pursuing an injection molding ceramic fabrication approach. This paper briefly overviews key features of the ceramic injection molding process, then describes the approach and methodology being used to fabricate PZT ceramic/polymer posites. Properties and applications of injection molded PZT ceramics are pared with conventionally processed material.IntroductionPiezoelectric ceramic/polymer posites offer design versatility and performance advantages over both single phase ceramic and polymer piezoelectric materials in both sensing and actuating applications. These posites have found use in high resolution medical ultrasound as well as developmental Navy applications. Many posite configurations have been constructed and evaluated on a laboratory scale over the past thirteen years. One of the most successful binations, designated 13 posite in Newnham’s notation [l 1, has a onedimensionally connected ceramic phase (PZT fibers) contained within a threedimensionally connected organic polymer phase. Hydrophone figures of merit for this posite can be made over 10,000 times greater than those of solid PZT ceramic by appropriately selecting the phase characteristics and posite structure.The Penn State posites were fabricated [ l ] by handaligning extruded PZT ceramic rods in a jig and encapsulating in epoxy resin, followed by slicing to the appropriate thickness and poling the ceramic. Aside from demonstrating the performance advantages of this material, the Penn State work highlighted the difficulties involved in fabricating 13 posites on a large scale, or even for prototype purposes. These are:1) The requirement to align and support large numbers of PZT fibers during encapsulation by the polymer.2) The high incidence of dielectric breakdown during poling arising from the significant probability of encountering one or more defective fibers in a typical large array. Over the past five years several attempts have been made to simplify the assembly process for 13 transducers with the intention of improving manufacturing viability and lowering the material cost. Early attempts involved dicing solid blocks of PZT ceramic into the desired configuration and backfilling the spaces with a polymer phase. This technique has industry for manufacturing high frequency transducers [2]. More recently, Fiber Materials Corp. has demonstrated the applicability of its weaving technology for fiberreinforced posites to the assembly of piezoelectric posites [31. Another exploratory technique involves replicating porous fabrics having the appropriate connectivity [4]. For extremely fine scale posites, fibers having diameters in the order of 25 to 100 pn and aspect ratios in excess of five are required to meet device performance objectives. As a result, these difficulties are pounded by the additional challenge of forming and handling extremely fine fibers in large quantities without defects. Recently, researcher