When 3:30 PM - 5:00 PM Sep 10, 2010
Where 1670 CSE
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Microstructure Design of Lead-Free Piezoelectric Ceramics


R. Edwin Garcia, Materials Engineering, Purdue University

The environmental premise to eliminate lead from commercial piezoelectric products has been greatly limited by the identification of chemistries and processing operations that deliver the same or better performance than the equivalent lead-containing materials. Current material design approaches comprise careful tuning of chemistries in the neighborhood of the morphotropic phase boundary, while searching for sophisticated microstructures that deliver macroscopic responses equivalent to the theorized single-crystal values. In this paper, a novel methodology is presented to analyze the effect of microstructure on the macroscopic piezoelectric response for polycrystalline BNKT ceramics. The method combines position-dependent EBSD data collection and FIBing to threedimensionally reconstruct the morphology, crystallographic orientation, and grain boundary misorientation of every grain. Reconstructed 3D representations of textured and untextured samples are used to generate a comprehensive numerical description that spatially resolves the polarization, elastic, and electromechanical fields. A Monte Carlo algorithm is combined with experimentally determined macroscopic MRD data to assign a statistically representative polarization axis for each ferroelastic domain. The predicted macroscopic response is directly compared against experimental data and further extended to predict optimal and experimentally accessible crystallographic and ferroelectric textures.

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