The widespread use of ceramics is generally limited due to their limited ductility and toughness, compromising their behavior as structural components. However, zirconia-based ceramics may be able to overcome this limitation thanks to a martensitic phase transformation from a tetragonal to a monoclinic phase. Recently, ceramic materials quite similar to shape memory alloys could be obtained, with a stress and/or temperature-controlled phase transformation as a source of plasticity. In particular, ceria-doped zirconia ceramics are of interest, since they do not suffer from low-temperature degradation, in contrast with the more commonly seen yttria-stabilized zirconia. Moreover, they transform at lower stresses, before crack initiation, making them suitable to develop larger ductility. However, the control of the transformation is still not fully described and more understanding on the critical stress allowing for plasticity and the effect of crystal orientation is needed. Therefore, the present work proposes to evaluate the martensitic phase transformation at small scale by combining experimental and numerical approaches.

For this, several single-crystalline micropillars with different orientations, composed of 12 mol% ceria-stabilized zirconia, were milled using Focused Ion Beam (FIB). Each pillar was compressed using a FT-NMT04 nano-indenter (FemtoTools) equipped with a diamond flat punch, where deformation was followed by Scanning Electron Microscopy (SEM). In addition, quasi-static compression simulations at the atomistic scale were carried out on quasi 2D-single-crystalline zirconia using a neural-network interatomic potential able to reproduce the relative stability and properties of zirconia phases.

By combining both works, a detailed understanding of the crystal orientation dependence of plastic deformation is obtained, as well as the determination of critical stresses for transformation.