硅酸盐学报

通过在1680℃热压烧结,氮和氩2种气氛下制备了SiC–Si3N4–Y2O3陶瓷材料样品,并采用X射线衍射仪分析了样品的相组成。结果表明:在SiC–Si3N4–Y2O3样品的系统中,除了SiC和Si3N4共存外,还生成了Si3N4·Y2O3(M),Si2N2O·Y2O3(K)和Si2N2O·2Y2O3(J)相。SiC和Si3N4都分别同这3相共存。Si2N2O组分的引入使系统扩大成为SiC–Si3N4–Si2N2O–Y2O3四元系。在此四元系统中分别确定了3个相容性四面体,即,SiC–M–K–J,SiC–M–J–Y2O3,SiC–Si3N4–M–K(N2气氛)或SiC–Si3N4–M–J(Ar气氛)。随着样品中配置粉料的氧含量和高温氛围氧分压的影响,SiC和Si3N4将依含氧量由低到高的顺序M,K,J,Y2O3,分别有选择性地与三相处于平衡。提出了SiC–Si3N4–Y2O3三元系统和SiC–Si3N4–Si2N2O–Y2O3四元系统亚固相图。

Samples of the SiC–Si3N4–Y2O3 system were sintered with N2 or Ar atmosphere under hot pressing (HP) at 1 680 ℃. The phase compositions of the HP sintered samples were analyzed by X-ray diffraction. The results show that either M phase (Si3N4·Y2O3), K phase (Si2N2O·Y2O3) or J phase (Si2N2O·2Y2O3) were formed with SiC and Si3N4 in the samples. The introduction of Si2N2O transformed the ternary system into a quaternary system. In the system, three compatible tetrahedrons, namely, SiC–M–K–J, SiC–M–J–Y2O3, SiC–Si3N4–M–K (in N2) or SiC–Si3N4–M–J (in Ar) have been determined. SiC and Si3N4 were selectively equili-brated with these three phases in the order of M, K, J, Y2O3 with respect to the effects of the oxygen content of SiC and Si3N4 powders and the oxygen partial pressure at high temperature. Based on these results, the subsolidus phase diagram for the ternary SiC–Si3N4–Y2O3 system and the quaternary SiC–Si3N4–Si2N2O–Y2O3 system are provided.