Oxygen Self‐diffusion in Cylindrical Single‐Crystal Mullite

A mixture of SiO 2 and Al 2 O 3 was prepared from metal alkoxides and fired at 1650°C to form mullite and an SiO 2 -rich glass phase. After leaching out the glass phase, crystalline mullite powder was obtained. Transmission electron microscopy examination revealed the powder to be cylindrical particles of single-crystal mullite. A diffusion experiment was performed on the mullite to determine the oxygen diffusion coefficient. This could be expressed as D ox = 1.32 × 10 -6 exp[-397 kJ/RT] m 2 s -1 in the range of 1100 to 1300°C. This falls along the line extended through the oxygen diffusion coefficient of forsterite, which is similar in crystal structure to mullite.