Ferroelastic domain switching toughening in Ce–Y–La co-stabilized zirconia ceramics obtained from coated starting powders

While ensuring good resistance to hydrothermal or high-temperature aging of zirconia ceramics, constant attempts to understand and improve their fracture toughness remain the focus. In this work, 0.1–0.3 mol.% of La 2 O 3 was doped into a 1.5 mol.% Y 2 O 3 +5.5 mol.% CeO 2 co-stabilized zirconia ceramic (C1.5Y5.5Ce) based on a coating route. Compared with conventional 3 mol.% Y 2 O 3 stabilized zirconia (C3Y), their microstructure, mechanical properties, and corresponding toughening mechanisms were studied by XRD , SEM, Raman spectroscopy , XPS and TEM . Non-transformable t’ zirconia phase was found in both Ce–Y and Ce–Y–La co-stabilized ceramics. Tetragonal to monoclinic (t-m) phase transformation toughening combined with ferroelastic domain toughening is considered to be the primary toughening mechanism of these ceramics. Doping of La 2 O 3 causes significant grain refinement, which increases the hardness and facilitates the ferroelastic domain switching. The oxygen vacancy concentration and the valence state of cerium are also affected, resulting in a change in the tetragonal stability. Although with a lower t-m transformation rate, the 0.3 mol.% La 2 O 3 doped C1.5Y5.5Ce possessing the smallest grain size shows a high fracture toughness of 10.17 MPa m 1/2 , which is about 23% higher than that of C3Y.