Ti3GaC2 and Ti3InC2: First bulk synthesis, DFT stability calculations and structural systematics

A simple methodology for identifying possible higher order M(n+1)AX(n) phases (n >= 2) from the chemical characteristics of known phases was developed. The method was used to identify two potential M(3)AC(2) phases Ti3GaC2 and Ti3InC2. After verifying that the n=1 MAX phases in these systems could be synthesised in bulk using a simple pressureless reactive sintering process, the new phases were synthesised using the same method. DFT calculations were used to test the thermodynamic stability of the new phases against the known competing phases within the same ternary systems. Both were found to be stable although Ti3InC2 only marginally so. Crystal structure refinements and comparison to other MAX phases revealed a linear increase in the c-axis length as a function of the atomic radius of the A element. (C) 2015 Elsevier Inc. All rights reserved.