Effects of substitutional defects on the thermal-physical properties of Gd₂Zr₂O₇ pyrochlores

Rare-earth pyrochlores, particularly Gd₂Zr₂O₇, have been proposed as promising candidates for the next-generation thermal barrier coatings (TBCs) due to their good structural stability, low thermal conductivities at high temperatures. In this work, systematic studies of the incorporation of Yb³⁺, Nd³⁺, La³⁺, Ti⁴⁺, Hf⁴⁺, Ce⁴⁺ into cation sites in Gd₂Zr₂O₇ has been investigated by density functional theory (DFT) calculations to explore the underlying mechanisms for modifying its thermal-physical properties. Among these doped cations, incorporation of oversized Ce⁴⁺ at the Zr-site leads to significantly smaller Young’s modulus, better ductility, smaller Debye temperature, and lower thermal conductivity. In particular, the thermal conductivity of Ce-doped Gd₂Zr₂O₇ decreases as large as 21 % with the complete Ce substitution based on the Clarke’s model. The incorporation of oversized Ce cations weakens the interatomic bonds, which is the main factor for the improved thermal-physical properties of Gd₂Zr_2-yCe_yO₇ pyrochlores. The results provide theoretical predictions of the behavior and performance of pyrochlores at high temperatures and may promote experimental investigation in the future.