Structural Evolution and Atom Clustering in β-SiAlON: β-Si6-zAlzOzN8-z.
SiAlON ceramics, solid solutions based on the Si3N4structure, 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 Si3N4and 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-Si3N4framework. The average and local structural evolution of highly phase-pure samples of β-Si6-zAlzOzN8-zwith 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-spinning27Al NMR experiments, coupled with detailed ab initio calculations of NMR spectra of Al in different AlOqN4-qtetrahedra (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.
Clayton
C
Cozzan
Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Kent J
http://orcid.org/0000-0002-8096-906X
KJ
Griffith
Geneva
G
Laurita
Jerry G
JG
Hu
Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Clare P
CP
Grey
Ram
http://orcid.org/0000-0001-5858-4027
R
Seshadri