Structural evolution, synthesis mechanism and thermal conductivity of (La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7 high-entropy ceramic prepared by concurrent chemical coprecipitation method

(La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7 (Ln2Zr2O7) ceramic powders with nanoscale were synthesized by concurrent chemical coprecipitation method. The thermal behaviors and structural evolution of Ln2Zr2O7 precursor were investigated. The synthesis mechanism and thermal conductivity of Ln2Zr2O7 ceramic were also discussed in detail. Results show that a kind of complex polymeric compound containing -[Zr–OH–Zr]- and -[Zr–OH-Ln]- network structure was formed in the as-synthesized Ln2Zr2O7 precursor, which directly transformed to Ln2Zr2O7 crystals through dehydroxylation and structural ordering during the calcination process. The bulk Ln2Zr2O7 ceramics have a lower thermal conductivity of 1.20–1.47 W/(m·K), which can be attributed to the high-entropy effect resulting from the introduction of multiple rare earth elements.