Microstructure, mechanical and thermo-physical properties of hot-pressed Al2O3-GdAlO3-ZrO2 ceramics with eutectic composition

A low cost chemical co-precipitation method was employed to fabricate nanoscale Al2O3-GdAlO3-ZrO2 powder with eutectic composition. A careful control of reaction conditions was required during the preparation. The synthesized nanopowders exhibited a particle size of 20-200 nm, and were highly dispersive and uniform. The results showed that calcination temperature had an important influence on the phase constituents of the nanopowders. With increasing the calcination temperature, a phase transformation from Ɵ-Al2O3 to α-Al2O3 and a thermal decomposition from Gd3Al5O12 (GdAG) to GdAlO3 and α-Al2O3 occurred in sequence. A calcination temperature of 1300 °C was needed for the crystallization of α-Al2O3. These nanosized powders were consolidated via hot pressing to produce a fully densified ceramic composite with eutectic composition. The Al2O3-GdAlO3-ZrO2 ceramic hot-pressed at 1500 °C exhibited a relative density of 99.4%, a flexural strength of 485 MPa and a fracture toughness of 6.5 MPa m1/2. The ceramic had a thermal conductivity of 1.9 W m K−1 at 1200 °C and a thermal expansion coefficient of 9.49 × 10−6 K−1 at 1100 °C.