Dual-phase high-entropy zirconate (La0.25Sm0.25Er0.25Ho0.25)2Zr2O7 with enhanced sintering resistance for thermal barrier coatings

High anti-sintering is critical for thermal barrier coatings operating under prolonged thermal exposure. Here, we report a dual-phase high-entropy zirconate, (La0.25Sm0.25Er0.25Ho0.25)2Zr2O7, with its average grain size increasing only from 1.17 to 2.83 μm after heat treatment at 1600 °C for 10–100 h, demonstrating outstanding high-temperature anti-sintering capability. Ab initio calculations reveal that decreasing rare-earth ionic radius increases the surface energy for both pyrochlore and defect fluorite phases, with the (110) facet identified as the most stable. The bond-length and charge density analyses further uncover a pronounced disparity in lattice distortion between the coexisting phases, with markedly broader metal–oxygen bond distributions in the defect fluorite structure than in the pyrochlore counterpart. This strong structural heterogeneity, together with abundant pyrochlore and defect fluorite interfaces, suppresses grain coarsening and highlights dual-phase high-entropy design as an effective strategy for tuning the sintering behavior of materials.