Effects of soluble Cr2O3 doping on the glass structure, microstructure, crystallization behavior, and properties of MgO-Al2O3-SiO2 sapphirine glass ceramics

Sapphirine glass ceramics were synthetized using small quantities of Cr2O3. The structure of the glass, transformation of the crystal phases, crystal growth behavior and physicochemical properties were investigated. Our results indicate that the content of Q3Si and Q4A1 gradually decreased, while the content of Q2Si, Q1Si, and Q3A1 increased within the parent glass during the addition of Cr2O3. The crystallization exothermic temperature of the parent glass decreased with addition of Cr2O3 and the main crystal phase of the resulting glass ceramic changed from alpha-cordierite to sapphirine. In Cr0 samples, square cordierite crystals of alpha-cordierite grew in the glass matrix. With Cr2O3 doped samples, pore-like (sapphirine-1A) and needle-like (sapphirine-2M) crystallographic morphology appeared. The addition of Cr2O3 was found to promote grain refinement of the sapphirine phase. Cr0.5 and Cr0.8 samples - with sapphirine as main crystal phase - can be used as medium thermal expansion material with a certain extent of strength and chemical resistance. In conclusion, the solid waste containing chromium can be used as raw material to prepare the sapphirine glass ceramics with a certain extent of strength, chemical resistance and thermal expansion coefficient.