Nb4AlC3:: A new compound belonging to the MAX phases

Nb4AlC3, a new compound belonging to the MAX phases, was discovered by annealing bulk Nb2AlC at 1700 degrees C. The crystal structure of Nb4AlC3 was determined by combined X-ray diffraction, high-resolution transmission electron microscopy and ab initio calculations. It was reported that Nb4AlC3 follows the Ti4AlN3-type crystal structure. The lattice constants are a = 0.31296 nm, c = 2.41208 nm and the atomic positions are Nb1 at 4f (1/3, 2/3, 0.0553), Nb2 at 4e (0, 0, 0.1574), Al at 2c (1/3, 2/3, 1/4), C1 at 2a (0, 0, 0) and C2 at 4f (2/3, 1/3, 0.1086). (c) 2007 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.