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2002
Journal Article
Titel
Investigation of the phase composition and stability of the alpha - SiAlONs by the Rietveld method
Abstract
Different compositions of Y- and Nd- alpha -SiAlONs were sintered at 1825 degrees C and analysed by the XRD method. The Rietveld technique was used for characterisation of the diffraction pattern and the x value of alpha -SiAlON, which has a composition of R/sub x//sup +v/Si/sub 12- (m+n)/Al/sub m+n/O/sub 16-n/ (R = Y, Nd). It was shown that the method yields reliable data for the content of the rare earth cations in the alpha-SiAlONs phase, even in mixtures of alpha -SiAlONs with beta - or alpha -Si/sub 3/N/sub 4/, but cannot be used for the determination of the Al and/or O contents of the alpha-SiAlONs. On the basis of these data, the stability regions of Y- and Nd-alpha-SiAlONs were established. Furthermore, it was found that the solubility area of the a- SiAlONs depends on the size of the additives. It was also shown that the solubility area of the Y- alpha -SiAlON is extended to lower X values than those suggested in the literature.