At-Temperature Observation of Phase Development in Yttrium α-Sialon

摘要

A powder mixture of α-Si_3N_4, AlN and Y_2O_3 corresponding to an yttrium α-sialon composition, Y_(0.4)Si_(10.2)Al_(1.8)O_(0.6)N_(15.4), was sintered both in a high temperature X-ray diffraction unit and in a regular sintering furnace. X-ray analysis was performed and it was shown that high temperature X-ray diffraction can be used to monitor the kinetics of the α-sialon phase formation during sintering at temperatures between 1450 and 1580℃ as the reactions take place. A variety of yttrium-rich intermediate and secondary phases are formed during sintering; those formed in the HT-XRD unit were not the same as those formed in the regular sintering furnace, but they do not significantly influence the overall reaction sequence or the amount of α-sialon formed. Quantitative analysis of the acquired data was used to evaluate the kinetics of the α-sialon phase formation; the estimated activation energy of the initial stage α-sialon formation was 330 kJ/mol. After this initial stage of relatively rapid α-sialon formation the process became inhibited.