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.

The Effect of Sintering Temperature on the Phase Composition, Microstructure, and Mechanical Properties of Yttria-Stabilized Zirconia

“…Obtaining rare earth-doped ZrO 2 with high sintering resistance and good phase stability is an urgent task to be solved by materials scientists who work in the field of high-temperature protective coatings. The authors [15] studied the effect of dopant species (La 2 O 3 , Nd 2 O 3 , Gd 2 O 3 , and Y 2 O 3 ) on the sintering resistance and phase stability of zirconiabased ceramics. When ZrO 2 was doped with the ions with larger radii (La 3+ , Nd 3+ , and Gd 3+ ), it exhibited improved sintering resistance at reduced tetragonal phase stability.…”

ZrO2 Matrix Toughened Ceramic Material‐Strength and Toughness

“…During the cooling process after sintering, the natural phase transformation from tetragonal phase to monoclinic phase occurs with large volume expansion, which may lead to cracks and other defects. [ 38,39 ] In order to obtain stable tetragonal phase at room temperature, stabilizers are added, such as Y 2 O 3 , [ 40,41 ] MgO, [ 42 ] CeO 2 , [ 43 ] CaO, [ 44,45 ] La 2 O 3 , [ 46 ] etc. The cations of Y 3 + , Mg 2 + , Ce 4 + , Ca 2 + , La 3 + can be partially dissolved into ZrO 2 ceramics, forming a substitutional solid solution, and preventing the spontaneous tetragonal‐monoclinic phase transition.…”

Thermal stability of MxOy‐doped zirconia aerogels (M = Y, Yb, Gd, Ce, Ca) studied through 1200°C

“…Modifying the dopant identity and concentration has been linked to changes in thermal conductivity and is established as a means of enabling advanced TBC material design 14–19 . A variety of rare earth dopant systems have been studied in the context of nanocrystalline zirconia, again with dopant identity and concentration changing the sintering and coarsening behavior of the materials 20–25 . Obtaining an understanding of how relevant kinetic and thermodynamic material properties, including surface energy, cation diffusivity, surface and grain boundary diffusivity, thermal conductivity, and more, in doped zirconia influence thermal stability will contribute to the development and understanding of a design framework to enable the intentional exploration of thermally stable aerogels.…”