EFFECT OF MgAl₂O₄ ON THE GROWTH OF β -Si₃Al₃O₃N₅ PREPARED BY CARBOTHERMAL REDUCTION BY NITRIDING

The β-Si₃Al₃O₃N₅ compound was experimentally prepared by carbothermal reduction by nitriding using pure SiO₂, Al₂O₃, C, and N₂. The effect of MgAl₂O₄ on the growth of β-Si₃Al₃O₃N₅ was investigated as a function of temperature and molar concentration of MgAl₂O₄. In this way, it was found that the formation of β-Si₃Al₃O₃N₅ when MgAl₂O₄ is present in concentrations lower than 13 wt. % occurs. However, when the MgAl₂O₄ concentration was as high as 25.6 wt. %, the formation of β-Si₃Al₃O₃N₅ compound was not attained and the formation of quaternary magnesium-rich SiAlON phases such as Mg-Si₄Al₂O₆N₄ was found. Moreover, the mechanistic steps during the consolidation of SiAlON type structures are presented and discussed.