Microstructure and mechanical properties of ceramics obtained from chemically co-precipitated Al2O3-GdAlO3 nano-powders with eutectic composition

An efficient and flexible chemical co-precipitation method has been used to synthesize nanoscale Al2O3-GdAlO3 powders with eutectic composition. The as-synthesized powders exhibit a highly dispersive and homogeneous distribution with an average particle size of 50 nm. The phase transition in the resulting powders strongly depends upon the calcination temperature. GdAlO3 undergoes complete crystallization after calcination at 1050 °C, however, the diffraction peaks of α-Al2O3 are found at a relatively high calcination temperature of at least 1300 °C. The fully-densified Al2O3-GdAlO3 ceramic with eutectic composition obtained by hot pressing the nanoscale powders at 1500 °C exhibits a room temperature flexural strength of 556 MPa, a Vickers hardness of 17.3 GPa and a fracture toughness of 7.5 MPa m1/2. The high temperature flexural strength of the as-sintered Al2O3-GdAlO3 ceramic is measured to be 515 MPa after bending tests at 1000 °C.