Effect of Ceria Doping on the Mechanical Properties and Phase Stability of Partially Samaria-Stabilized Zirconia Crystals

The effect of ceria doping of (ZrO₂)_1−x(Sm₂O₃)_x crystals on their phase composition, microhardness and fracture toughness was studied. The (ZrO₂)_0.995−x(Sm₂O₃)_x(CeO₂)_0.005 crystals (where x = 0.032, 0.037 and 0.04) were grown using directional melt crystallization in a cold crucible. The mechanical properties, such as microhardness and fracture toughness, were explored using Vickers indentation. It was shown that the (ZrO₂)_0.995−x(Sm₂O₃)_x(CeO₂)_0.005 solid-solution crystals contained both Ce⁴⁺ and Ce³⁺ ions. Phase analysis data suggested that CeO₂ doping increased the tetragonality degree of the transformable t phase and reduced the tetragonality degree of the non-transformable t’ phase as compared to the (ZrO₂)_1−x(Sm₂O₃)_x crystals. As a result, the t→m phase transition triggered by the indentation-induced stress in the CeO₂-doped crystals was more intense and covered greater regions. CeO₂ doping of the solid solutions increased the fracture toughness of all the crystals studied, whereas the microhardness of the crystals changed only slightly. CeO₂ doping of the (ZrO₂)_1−x(Sm₂O₃)_x solid solutions in the experimental concentration range did not improve the high-temperature phase stability of the crystals and did not prevent high-temperature degradation of their fracture toughness.