Influence of Thermal Decomposition on the Mechanical Properties of Magnesia‐Stabilized Cubic Zirconia

Cubic magnesia‐stabilized zirconia was decomposed by isothermal heat treatment at 1100°C. The mechanical properties, including strength, fracture toughness, and hardness, were measured at various stages during the decomposition process. The strength initially decreased with aging but then recovered almost to its initial value. This strength decrease was associated with cracking of islands of the cubic phase in the matrix of monoclinic zirconia. The fracture toughness followed the strength although it was found that the monoclinic phase exhibited stable crack growth during notched beam fracture experiments or R ‐curve behavior. Measurements of the hardness indicated that the cubic phase was much harder than the monoclinic phase. In addition, X‐ray diffraction, optical, and transmission electron microscopy studies were made of the decomposition process.