Effect of doping rare earth oxides (RE= Sc, Y, Gd, Eu) on structural, thermal and mechanical properties of La2(Zr0.7Ce0.3)2O7 ceramics

Rare-earth (RE) oxide-doped La2(Zr0.7Ce0.3)2O7 (LZC) has attracted great interest in thermal barrier coatings (TBCs) because of its lower thermal conductivity. However, studies on the laws governing the effect of different types of RE oxide doping on the performance of LZC ceramics are limited. Therefore, in this study, different types of RE (Sc, Y, Gd and Eu) doped LZC ceramic bulks have been prepared using solid phase reaction method. The effects of RE doping on the crystal structure, mechanical properties and thermal properties of the LZC ceramics were investigated. The results indicated that all five ceramics exhibited a single pyrochlore phase structure, whereas their lattice constants were reduced after doping, with (La0.85Sc0.15)2(Zr0.7Ce0.3)2O7 having the lowest lattice constant. The effect of rare earth doping on the grain growth of LZC was not evident; however, it could significantly improve the hardness of LZC. In addition, doping with all four RE ions significantly reduced the thermal conductivity of the LZC ceramics, and the most significant reduction was observed for Gd3+ doping.