The influence of the molar ratio of Al_2O_3 to Y_2O_3 on sintering behavior and the mechanical properties of a SiC-Al_2O_3-Y_2O_3 ceramic composite

摘要

The influence of the molar ratio of Al_2O_3 to Y_2O_3 (i.e. M_(Al_2O_3)/M_(Y_2O_3)) on sintering densification, microstructure and the mechanical properties of a SiC-Al_2O_3-Y_2O_3 ceramic composite were studied. It was shown that the optimal value of M_(Al_2O_3)/M_(Y_2O_3) was 3/2, not 5/3, which is customarily considered the optimal molar ratio for the formation of YAG (Y_3Al_5O_(12)) phase. When M_(Al_2O_3)/M_(Y_2O_3) is 5/3, materials existed in two phases of YAG and very little YAM phases. The sintering mechanism of the solid phase occurred at 1850℃. When M_(Al_2O_3)/M_(Y_2O_3) was 3/2, materials existed in the two phases YAG (Y_3Al_5O_(12)) and YAM (Y_4Al_2O_9). The formation of the low melting point eutectic liquid phase (YAG + YAM) increased sintering densification. Flexure strength, hardness and relative density were all higher.