Experimental synthesis and density functional theory investigation of radiation tolerance of Zr ₃ (Al _1‐ <scp> _x S </scp> i _x )C ₂ <scp>MAX</scp> phases

Abstract

Abstract Synthesis, characterization and density functional theory calculations have been combined to examine the formation of the Zr 3 (Al 1– x S i x )C 2 quaternary MAX phases and the intrinsic defect processes in Zr 3 AlC 2 and Zr 3 SiC 2 . The MAX phase family is extended by demonstrating that Zr 3 (Al 1– x S i x )C 2 , and particularly compositions with x ≈0.1, can be formed leading here to a yield of 59 wt%. It has been found that Zr 3 AlC 2 ‐ and by extension Zr 3 (Al 1– x S i x )C 2 ‐ formation rates benefit from the presence of traces of Si in the reactant mix, presumably through the in situ formation of Zr y Si z phase(s) acting as a nucleation substrate for the MAX phase. To investigate the radiation tolerance of Zr 3 (Al 1– x S i x )C 2 , we have also considered the intrinsic defect properties of the end‐members. A ‐element Frenkel reaction for both Zr 3 AlC 2 (1.71 eV ) and Zr 3 SiC 2 (1.41 eV ) phases are the lowest energy defect reactions. For comparison we consider the defect processes in Ti 3 AlC 2 and Ti 3 SiC 2 phases. It is concluded that Zr 3 AlC 2 and Ti 3 AlC 2 MAX phases are more radiation tolerant than Zr 3 SiC 2 and Ti 3 SiC 2 , respectively. Their applicability as cladding materials for nuclear fuel is discussed.