Experimental synthesis and density functional theory investigation of radiation tolerance of Zr₃(Al₁–ₓ,Siₓ)C₂ MAX phases

Abstract

Synthesis, characterisation and density functional theory calculations have been combined to examine the formation of the Zr 3 (Al 1–x Si 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 Si x )C 2 , and particularly compositions with x ≈ 0.1, can be formed leading here to a yield of 59 wt.%. It has b een found that Zr 3 AlC 2 – and by extension Zr 3 (Al 1–x Si x )C 2 – formation rates benefit from the presence of tra ces 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 investig ate the radiation tolerance of Zr 3 (Al 1– x Si x )C 2 we have also considered the intrinsic defect prope rties 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 c onsider 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.