Theoretical Prediction and Synthesis of (Cr2/3Zr1/3)2AlC i-MAX Phase.

Guided by predictive theory, a new compound with chemical composition (Cr2/3Zr1/3)2AlC was synthesized by hot pressing of Cr, ZrH2, Al, and C mixtures at 1300 °C. The crystal structure is monoclinic of space group C2/ c and displays in-plane chemical order in the metal layers, a so-called i-MAX phase. Quantitative chemical composition analyses confirmed that the primary phase had a (Cr2/3Zr1/3)2AlC stoichiometry, with secondary Cr2AlC, AlZrC2, and ZrC phases and a small amount of Al-Cr intermetallics. A theoretical evaluation of the (Cr2/3Zr1/3)2AlC magnetic structure was performed, indicating an antiferromagnetic ground state. Also (Cr2/3Hf1/3)2AlC, of the same structure, was predicted to be stable.