The effect of Ba2+ on the crystallization thickness of calcium hexaaluminate (CA6) along the c axis was studied. The results show that after introduction of Ba2+, the CA6 flake crystals fired at 1600°C become thicker obviously. The structure refinement shows that the structure formula of the doped CA6 is (Ca0.973Ba0.027)O·6Al2O3, indicating Ba2+ has entered the lattices of CA6 and substituted Ca2+ in the mirror layers. The introduction of Ba2+ results in more defects VAl in spinel block layers in CA6, making ions easier to diffuse along c axis and fastening the growing of CA6 crystals along c axis. Thus, the introduction of Ba2+ is feasible and advantageous to increase the crystallization thickness of CA6 along c axis.

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Al 4 SiC 4 powders with high purity were synthesized by heating the powder mixture of aluminum (Al), silicon (Si), and carbon (C) at 1800°C in argon. The microstructure is characterized as platelike single grain. Both the nonisothermal and isothermal oxidation behavior of Al 4 SiC 4 was investigated at 800°C-1500°C in air by means of thermogravimetry method. It is demonstrated that Al 4 SiC 4

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Abstract. The hercynite synthesized at 1600C in protection atmosphere was thermogravimetrically analyzed. The results show that the change of oxygen partial pressure during sintering transformssome Fe