Thursday, June 23, 2011

Crystal Habits: Crystallography in the SEM

The ability to image crystal habits can be of great utility in identifying phases. The top BEI image shows SnO2 deposited on Al2O3 using PVD with Ar as a carrier gas. EDS determined these structures to all be either Sn or SnOx. SnO2 is a tetragonal system that tends towards prismatic. acicular and botryoidal crystals. Toward the center of the image is what appears to be perfect bipyramids consistent with a tetragonal system. The spherical objects have what appear to be hints of facets. (Thanks to Dr. Peng Xiong, FSU Department of Physics.)

The the bottom SEI image shows a cluster of pyrite pyritohedra-- irregular dodecahedra-- clustered together in a clay mineral sample. The phase identification was immediate upon observation and confirmed using EDS spectroscopy.
(Thanks to Dr. Woody Wise, FSU Department of Earth, Ocean and Atmospheric Science.)

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