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

Abstract

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.