The grain-boundary microcracking materials in the system Al₂TiO 5 -ZrTiO₄ (ZAT) is influenced by the thermal expansion anisotropy. The range of ZAT compositions investigated had showed very low thermal expansions of 0.3∼1.3×10 -6 /K compared to 8.29×10 6 /K pure ZrTiO4 and 0.68×10 6 /K of polycrystalline Al₂TiO 5 , respectively, compared with the theoretical thermal expansion coefficient for a single crystal of Al₂TiO 5 , 9.70×10 6 K. The low thermal expansion and microcraking temperature are apparently due to a combination of thermal contraction and expansion caused by the large thermal expansion anisotropy of the crystal axes of the Al₂TiO 5 phase.