Synthesis and characterization of MgAl2O4–ZrO2 composites

Different types of dense 5–97% ZrO2–MgAl2O4 composites have been prepared using a MgAl2O4 spinel obtained by calcining a stoichiometric mixture of aluminium tri-hydroxide and caustic MgO at 1300 °C for 1 h, and a commercial yttria partially stabilized zirconia (YPSZ) powder as starting raw materials by sintering at various temperatures ranging from 1500 to 1650 °C for 2 h. The characteristics of the MgAl2O4 spinel, the YPSZ powder and the various sintered products were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface area, particle size analysis, Archimedes principle, and Vickers indentation method. Characterization results revealed that the YPSZ addition increases the sintering ability, fracture toughness and hardness of MgAl2O4 spinel, whereas, the MgAl2O4 spinel hampered the sintering ability of YPSZ when sintered at elevated temperatures. A 20-wt.% YPSZ was found to be sufficient to increase the hardness and fracture toughness of MgAl2O4 spinel from 406 to 1314 Hv and 2.5 to 3.45 MPa m1/2, respectively, when sintered at 1600 °C for 2 h.