Crystal Chemistry of Boehmite

Rodney Tettenhorst and Douglas A. Hofmann1
Department of Geology and Mineralogy, The Ohio State University, Columbus, Ohio 43210
1 Present address: Owens-Coming Fiberglas Corporation, Granville, Ohio 43023.

Abstract: Thirty two boehmites, synthesized at temperatures ranging from room temperature to 300°C were examined by scanning electron microscopy, transmission electron microscopy, electron diffraction, X-ray powder diffraction, differential thermal analysis, and infrared spectroscopy. The results show that boehmite exhibits a continuous gradation in crystallite size ranging from single octahedral layers or a few unit cells to about 65 unit cells in the y-direction. This conclusion suggests that the term pseudoboehmite is inappropriate for finely crystalline boehmite. Finely crystalline boehmite contains more sorbed water than coarsely crystalline boehmite; this water is commonly intercalated between octahedral layers, usually randomly but sometimes regularly. The regularly interstratified boehmite gives rise to a diffuse “long spacing” X-ray diffraction reflection. Calculated 020 X-ray diffraction peaks approximate closely those observed experimentally when a range of crystallite sizes is taken into account.

Key Words: Boehmite • Crystallite size • Pseudoboehmite • Synthesis • X-ray powder diffraction

Clays and Clay Minerals; October 1980 v. 28; no. 5; p. 373-380; DOI: 10.1346/CCMN.1980.0280507
© 1980, The Clay Minerals Society
Clay Minerals Society (www.clays.org)