Offre de thèse – INSA Lyon

The vast majority of ceramics exhibit, as a first very good approximation, an elastic-brittle behavior at
room temperature. They therefore break before reaching their elastic limit. This is linked to the very low
mobility of dislocations at room temperature, which compromises any ductility by movement of
dislocations as is observed in metals. However, some zirconia-based ceramics can exhibit real plasticity at
room temperature, thanks to a stress-induced martensitic phase transformation mechanism which is
similar in several ways to the TRIP (‘TRansformation Induced Plasticity’) mechanism observed in certain
steels and/or the ‘shape memory’ effects of certain metal alloys. This behavior is particularly remarkable in
zirconia doped with cerium oxide, which exhibit plastic deformations of the order of one percent before
rupture, high toughness (for ceramics), and lower sensitivity to the presence of defects than classic
ceramics. The NANOTRIP project proposes a study of the physical processes that control this TRIP effect
at the nanoscale in these zirconia, with the aim of designing ceramics with improved ductility and
toughness, as well as a « shape memory » effect. The methodology proposed in the NANOTRIP project
bases both on modeling approaches (ab initio, molecular dynamics) and on in-situ experiments, with the
latter being the subject of this thesis.