Structure characterization and mechanical properties of CeO2–ZrO2 solid solution system

The measured and calculated lattice parameters, microstructures, and mechanical properties (fracture toughness and microhardness) of CeO2–ZrO2 system ceramics are investigated, using CeO2–ZrO2 solid solution powder prepared by a microwave-induced combustion process. The CeO2–ZrO2 solid solution ceramics were sintered at 1500 °C for 6 h in air; the density of all specimens was greater than 94% of the theoretical density. For Ce1−xZrxO2 (0.00 ≦ x ≦ 0.50), the measured lattice parameter is in accordance with that of Kimʹs doped CeO2 model. On the other hand, for x ≧ 0.50, the measured values fit Kimʹs doped ZrO2 model. The fracture toughness and microhardness of CeO2–ZrO2 system ceramics with various compositions were investigated with Vickers indentation. The results showed that the crack mode of CeO2–ZrO2 solid solution was Palmqvist cracks under loads of 1 kg. Generally, the fracture toughness should increase with grain size at the submicron scale. However, larger grains may lead to spontaneous transformation, which should decrease the potential toughening at room temperature. This behavior was observed in the Ce0.25Zr0.75O2 ceramic, which demonstrated a high fracture toughness that may be ascribed to two causes: (1) fine grain size and (2) transformation toughening.