Investigation of the phase composition and stability of the α-SiAlONs by the Rietveld method

Different compositions of Y- and Nd-α-SiAIONs were sintered at 1825 °C and analysed by the XRD method. The Rietveld technique was used for characterisation of the diffraction pattern and the x value of α-SiAION, which has a composition of content of the rare earth cations in the α-SiAION phase, even in mixtures of α-SiAIONs with β- or α-Si₃N₄, but cannot be used for the determination of the A1 and/or O contents of the α-SiAIONs. On the basis of these data, the stability regions of Y- and Nd-α-SiAIONs were established. Furthermore, it was found that the solubility area of the α-SiAIONs depends on the size of the additives. It was also shown that the solubility area of the Y-α-SiAION is extended to lower X values than those suggested in the literature.