Springer Online Journal Archives 1860-2000
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Abstract The crystal structures of calcium and yttrium containingα-sialons, M x (Si, Al)12(N, O)16, were refined by the Rietveld analysis of their X-ray powder diffraction patterns. Rather lowR factors obtained in the refinements provide conclusive evidence for a structural model proposed by the Newcastle group. In theseα-sialons, the modifying cations occupy large closed interstices of the (Si, AD-(N, O) network similar structurally to that inα-Si3N4; each cation is coordinated to seven (N, O) atoms with an average M-(N, O) length of ∼0.26nm. The (Si, Al)-(N, O) bonds range in distance from 0.17 to 0.18nm (average 0.176 nm). The Rietveld method has been shown to give highly accurate occupation factors for the interstitial cations.
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