<title>Next-generation electroceramic fibers for active control</title>

Abstract

Lead-based PMN-3 1PT (O.69Pb(Mg113Nb213)03-O.3 lPbTiO3) and lead-free BNBZT (Zr doped fibers in the 250-500 micrometer diameter range were produced using CeraNova's proprietary extrusion technology.Various recrystallization approaches were investigated, including seeded solid state conversion and self-seeded texturing, with the goal of obtaining single-crystalline or textured macrocrystalline fibers. Grains in excess of 100 micrometersand exceeding 1 mm in some cases -with surface and bulk coverage approaching 1 00%, were obtained in a narrow temperature range and under carefully controlled atmosphere conditions. Large grain growth in BNBZT required the presence of BaSrTiO3 or SrTiO3 seeds and temperatures in the 1 1 50-1200°C range. In PMN-31PT, nearly complete recrystallization was observed in unseeded material at relatively low temperature (1000°C) and short time (one hour), and improved performance was achieved with a two-step sintering schedule and slightly extended time. While conduction effects have not yet allowed complete assessment of recrystallized BNBZT, PMN-3 1PT fibers have shown excellent piezoelectric properties with remanent polarization in excess of 3OtC/cm2 and coercive field of 4.5kV/cm. When incorporated into active fiber composites, the latter fibers' performance of 2000 microstrain is superior to average PZT-based production composites. Efforts are under way to induce preferred orientation in the large crystals in order to maximize performance. This work is funded by the Single Crystal Fiber Composites DARPA contract F49620-99-2-0332.