Thermal expansion and mechanical properties of self-reinforced aluminum titanate ceramics with elongated grains

To fabricate aluminum titanate ceramics that possess both low thermal expansion coefficients and excellent mechanical properties, the co-doping of MgO with Y2O3, La2O3 and Nb2O5 was examined. Doping with MgO lowered the formation reaction temperature of aluminum titanate and prevented the formation of oriented grain regions. Liquid-phase sintering at 1500 °C of the MgO-La2O3-doped ceramic resulted in the formation of a minor amount of elongated grains with lengths of approximately 130 μm. This microstructure resulted in a high resistance against crack propagation during the bend test. Grain pull-out and grain bridging mechanisms as well as crack deflection and branching resulted in the high resistance. A low thermal expansion coefficient of 0.7 × 10−6/deg was observed for this ceramic. The co-doping of MgOY2O3 led to high bending strength and moderate low thermal expansion coefficient. The co-doping of MgO-Nb2O5 resulted in an extended grain growth by liquid-phase sintering at 1500 °C and poor mechanical properties.