MAX phases Hf2(SexS1−x)C (x = 0–1) and their thermal expansion behaviors

Herein, a series of chalcogen-containing MAX phases, Hf2(SexS1−x)C, were successfully synthesized, whose lattice parameter change follows the Vegard’s law. The average coefficient of thermal expansion (CTE) can be continuously tuned from 7.59 μK−1 to 9.93 μK−1 when the occupancy rate x of Se changes from 0 to 1. The substitution of Se for S effectively soften the crystal structures that is reflected by long average M-A bond in Se-alloying Hf2(SexS1−x)C. However, the CTEs along a and c axes in all Hf2(SexS1−x)C MAX phases are almost same which may be find application in thermal barrier coating (TBC) that isotropic volume change is highly demanding.