Extruded electroactive fibers: preferred crystallographic orientation

Abstract

Electroactive fibers of preferred macro crystalline orientation and ultimately single crystal structure are goals of the research discussed in this paper. Four compositions are under evaluation; lead magnesium niobate4ead titanate solid solution, PMN-3 IPT, an incongruently melting near-morphotropic phase boundary piezoelectric composition; PMN-1OPT, an electrostrictor composition; and two lead free compositions in the sodium bismuth titanate-barium titanate solid solution, NBiT-BaT, family, both congruently melting, one electrostrictor and one piezoelectric. The efficacy of seed crystals in stimulating oriented crystal growth is being evaluated in the lead-based PMN-31PT system. Sub-micron reactive precursor powders of high chemical potential are being evaluated as matrix material. Direct fiber and ribbon extrusion have been shown to orient prismatic, needle and platelet shaped seed crystals. Extrusion orifice, seed and initial matrix particle size have not influenced the degree of seed orientation within the tested bounds of our experimental parameters. Non-equilibrium sintering conditions near the melting points of all four compositions noted above will be used to generate exaggerated grain growth under seeded and selfseeding conditions. In the PMN-3 1PT system, an as yet uncharacterized melt phase appears to stimulate rapid crystal growth, the orientation of which shall be determined by xray back reflection Laue methods. Analyses of fiber composition and grain orientation are ongoing. Results to-date will be reported. Analyses of fiber quality and performance, measured using single fiber P-E loop testing, are presented. Loops of sufficient quality to warrant fiber evaluation in active fiber composite packs have been measured. Progress toward program goals is summarized in this paper.