AVS 51st International Symposium
    Advanced Surface Engineering Monday Sessions
       Session SE-MoA

Paper SE-MoA3
Investigation of the Solubility in (M@sub x@M'@sub 2-x@)AlC (M and M' = Ti, V, Cr) as well as the Cr-Al-C System

Monday, November 15, 2004, 2:40 pm, Room 303D

Session: Structure Control of Hard Coatings in Sputtering Processes
Presenter: J.M. Schneider, RWTH Aachen, Germany
Authors: J.M. Schneider, RWTH Aachen, Germany
D. Music, RWTH Aachen, Germany
Z. Sun, RWTH Aachen, Germany
R. Mertens, RWTH Aachen, Germany
R. Ahuja, Uppsala University, Sweden
Correspondent: Click to Email
We have performed theoretical studies of the solubility within (M@sub x@M'@sub 2-x@)AlC, where M and M' = Ti, V, Cr by means of ab initio total energy calculations. The theoretical values of equilibrium volume and the optimized c/a ratios are in good agreement with those of experiments (within ~ ± 4% and ~ ± 1.3%, respectively). Furthermore, we show that if x is increased from 0 to 2 the bulk modulus can be increased by as much as 36%. Based on the total density of states analysis as well as the energy of formation, we suggest that the investigated systems show solubility except for the (Cr,Ti)@sub 2@AlC system. In addition to these data we have studied the effect of the chemical composition on the structure in the system Cr-Al-C by combinatorial thin film synthesis. By changing the Cr/C ratio from 1.72 to 3.48 and the Cr/Al ratio from 1.42 to 4.18 the formation of Cr@sub 2@AlC, Cr@sub 2@Al and Cr@sub 23@C@sub 6@ phases was observed. Furthermore, based on X-ray diffraction a single phase Cr@sub 2@AlC composition region is identified (Cr/C ratio between 1.72 and 1.925, Cr/Al ratio between 1.42 and 2.03) in the Cr-Al-C phase diagram. Throughout the studied composition range the lattice parameters of Cr@sub 2@AlC were independent of the chemical composition : a = 2.865 Å ± 0.2%, c = 12.80 Å ± 0.6%. Furthermore, we find that a deviation from the stoichiometric composition of up to 6.3 at % for Al still results the formation of a Cr@sub 2@AlC single phase field. Possible pathways to accommodate the observed deviation from stoichiometry are discussed.