Electrical properties of iron aluminides

Electrical properties of iron aluminides covering a wide range of Al contents have been investigated using a four-probe electrical resistivity method at room temperature. Room temperature electrical resistivities of iron aluminides indicate a monotonic increase with Al content up to ∼ 33 at.% Al, followed by a steep decrease with further increase of Al content. Heat treatments in a vacuum at 1100°C for 1 h, and at 700°C for 2 h followed by cooling to room temperature in helium and argon exhibited an identical trend, with resistivity values comparable to the values obtained after a prolonged annealing. A similar trend was observed with the fine grained sheets of FeAl obtained by roll compaction and sintering. Interpretation of literature band calculations with the help of the Mott and Jones model suggests that the electrical resistivity should increase with an increase in Al content until ∼ 33 at.% Al is reached, due to the filling up of holes by the electrons from Al in the narrow d-bands. Further addition of Al above 33 at.% value essentially adds more electrons to a nearly free electron conduction band and the resistivity falls sharply thereafter approaching the resistivity of Al.