Effect of rare earth elements on stability and sintering resistance of tetragonal zirconia for advanced thermal barrier coatings

The effect of dopant species on the sintering resistance of zirconia-based ceramics remains a huge challenge in terms of both experiment and theory. As one of the most popular materials for high-temperature protective coatings, it is still urgent to obtain rare earth-doped ZrO₂ with high sintering resistance and good phase stability. Here, the sintering resistance and phase stability of rare earth oxides (La₂O₃, Nd₂O₃, Gd₂O₃, and Y₂O₃)-stabilized zirconia (ZrO₂) were thoroughly studied by theoretical and experimental methods. According to experimental data, ZrO₂ doped with rare earth ions with larger radii (La³⁺, Nd³⁺, and Gd³⁺) exhibited improved sintering resistance at reduced tetragonal phase stability. Molecular dynamics simulation results revealed that rare earth ions with larger ionic radii are prone to segregation at grain boundaries, which can more effectively reduce the grain boundary energy in the materials under consideration. Therefore, the proposed approach involving doping of NdO₁.₅ (~1 mol%) and YO₁.₅ (YbO₁.₅, 6 mol%) in ZrO₂ is considered to be a promising route for the effective preparation of sinter-resistant ZrO₂-based ceramics for refractory and thermal barrier materials.