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Structural Evolution and Atom Clustering in β-SiAlON: β-Si$_{6-z}$Al$_z$O$_z$N$_{8-z}$

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Cozzan, C 
Griffith, KJ 
Laurita, G 
Hu, JG 
Grey, CP 


SiAlON ceramics, solid solutions based on the Si3N4 structure, are important, lightweight structural materials with intrinsically high strength, high hardness, and high thermal and chemical stability. Described by the chemical formula β-Si6−zAlzOzN8−z, from a compositional viewpoint, these materials can be regarded as solid solutions between Si3N4 and Al3O3N. A key aspect of the structural evolution with increasing Al and O (z in the formula) is to understand how these elements are distributed on the β-Si3N4 framework. The average and local structural evolution of highly phase-pure samples of β-Si6−zAlzOzN8−z with z = 0.050, 0.075, and 0.125 are studied here, using a combination of X-ray diffraction, NMR studies, and density functional theory calculations. Synchrotron X-ray diffraction establishes sample purity and indicates subtle changes in the average structure with increasing Al content in these compounds. Solid-state magic-angle-spinning 27Al NMR experiments, coupled with detailed ab initio calculations of NMR spectra of Al in different AlOqN4−q tetrahedra (0 ≤ q ≤ 4), reveal a tendency of Al and O to cluster in these materials. Independently, the calculations suggest an energetic preference for Al-O bond formation, instead of a random distribution, in the β-SiAlON system.



3402 Inorganic Chemistry, 34 Chemical Sciences

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Inorganic Chemistry

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American Chemical Society
C.C. thanks the National Science Foundation for a Graduate Research Fellowship under Grant DGE 1144085. K.J.G. thanks The Winston Churchill Foundation of the United States and the Herchel Smith Scholarship for funding. Use of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE), Office of Science, by Argonne National Laboratory, was supported by the U.S. DOE under Contract DE-AC02-06CH11357. DFT calculations were performed on the Darwin Supercomputer of the University of Cambridge High Performance Computing Service (, provided by Dell Inc. using Strategic Research Infrastructure Funding from the Higher Education Funding Council for England and funding from the Science and Technology Facilities Council (U.K.). This work made use of MRL-shared experimental facilities, supported by the MRSEC Program of the NSF under Award DMR 1121053. The MRL is a member of the NSF-funded Materials Research Facilities Network (