Phase Stability of Nanolaminated Epitaxial (Cr1-xFex)2AlC MAX Phase Thin Films on MgO(111) and Al2O3 (0001) for Use as Conductive Coatings

In this study, we model the chemical stability in the (Cr1-xFex)(2)AlC MAX phase system using density functional theory, predicting its phase stability for 0 < x < 0.2. Following the calculations, we have successfully synthesized nanolaminated (Cr1-xFex)(2)AlC MAX phase thin films with target Fe contents of x = 0.1 and x = 0.2 by pulsed laser deposition using elemental targets on MgO(111) and Al2O3 (0001) substrates at 600 degrees C. Structural investigations by X-ray diffraction and transmission electron microscopy reveal MAX phase epitaxial Iilms on both substrates with a coexisting (Fe,Cr)(5)Al-8 intermetallic secondary phase. Experiments suggest an actual maximum Fe solubility of 3.4 at %, corresponding to (Cr0.932Fe0.068)(2)AlC, which is the highest Fe doping level achieved so far in volume materials and thin films. Residual Fe is continuously distributed in the (Fe,Cr)(5)Al-8 intermetallic secondary phase. The incorporation of Fe results in the slight reduction of the c lattice parameter, while the a lattice parameter remains unchanged. The nanolaminated (Cr0.932Fe0.068)(2)AlC thin films show a metallic behavior and can serve as promising candidates for highly conductive coatings.

Automated summary

In this study, chemical stability in the (Cr1-xFex)(2)AlC MAX phase system was modeled using density functional theory, and nanolaminated (Cr1-xFex)(2)AlC MAX phase thin films were successfully synthesized with different Fe contents. Experimental results revealed a maximum Fe solubility of 3.4 at % and metallic behavior in the thin films, making them promising candidates for highly conductive coatings.