Ti_5Al_2C_3: A New Ternary Carbide Belonging to MAX Phases in the Ti-Al-C System

摘要

A new compound, Ti_5Al_2C_3, is identified in the bulk sample prepared by reactive hot pressing a mixture of Ti, Al and graphite powders with a nominal molar ratio of Ti:Al: C = 5:2.15:2.78 at 1580℃ for 1 h. This compound follows the crystal structure of other MAX phases. The lattice parameters are a = 0.3038 nm, c = 3.2261 nm, and the atomic positions are Ti_1 at 4/ (1/3, 2/3, 0.0208), Ti_2 at 4/ (1/3, 2/3, 0.1778), Ti_3 at 2d (2/3, 1/3, 0.25), Al at 4e (0, 0, 0.1035), C_1 at 2a (0, 0, 0), and C_2 at 4e (0, 0, 0.2102).