Opportunities for improved TBC durability in the CeO2–TiO2–ZrO2 system

A previously unreported, relatively large single-phase tetragonal field with exceptional tetragonality has been stabilized up to at least 1350 °C by co-doping zirconia (ZrO2) with ceria (CeO2) and titania (TiO2). The tetragonality is believed to be responsible for an increase in micro-indentation toughness, relative to traditional 7YSZ, based on activation of ferroelastic domain switching. Evidence consistent with this toughening mechanism has been directly observed via transmission electron microscopy (TEM). Within grains > 5 μm, long-range anion order is induced within elastically switched domains. This observation provides additional insight on the toughening mechanism. In the absence of stoichiometric anion vacancies, the large non-transformable tetragonal composition range and the improved toughness suggest that this system could be a promising option for next generation thermal barrier coatings.

► Ceria–titania doped zirconia is a promising alternative for next generation TBCs.
► Ce4 + and Ti4 + cations stabilize a nontransformable tetragonal phase.
► The tetragonal phase is stable up to at least 1350 °C.
► Measurable improvements in toughness are associated with the high tetragonality.
► Insights on the ferroelastic toughening mechanism are also discussed.