Aluminum titanate belongs to orthorhombic pseudo-brookite (Fe2TiO5, Pseudobrookite) type crystal. The thermal expansion coefficients in the crystal axis directions are αa=11.8×10-6/°C, αb=19.4×10-6/°C, and αc=-2.6×10-6/°C, respectively. Based on this, the average thermal expansion coefficient was calculated to be 9.5×10-6/°C, which is larger than that of α-type aluminum oxide. Aluminum titanate ceramics are well-known materials with low thermal expansion coefficient, but they are easy to crack when calcined at high temperature and have poor mechanical strength. In addition, aluminum titanate is easily decomposed into oxides when heated at about 1000°C, and easily converted into other compounds in a reducing atmosphere.