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Strengthening of ZrO2 Ceramics due to Nano-Crystallization

The fracture strength σf of ZrO2-based ceramics tends to increase with decreasing grain size d. As compared with the data for submicrometer-grain-sized material with d ≈ 350 nm, nano-crystallization of ZrO2 ceramics less than d ≈ 90 nm can improve σf by a factor of 2.0-2.5. The maximum strength reaches σf ≈ 2500 MPa, which is classed as the highest σf of oxide ceramic materials. The high σf can be associated with an increase in the critical t →m transformation stress and a decrease in the flaw size due to nano-crystallization.