Crystal Structure Transformation in Fe_2VSi and Its Substituted Compounds

Abstract

X-ray powder diffraction and thermal expansion measurements were made for the Fe₂V_1-xT_xSi (T=Mn, , Cr) compounds below room temperature. With decreasing temperature T, the intermetallic Fe₂VSi compound (x=0) shows the first order transition from the cubic L2₁-type to the tetragonal structure at -- 120, K, at which the lattice expands by nearly 1× 10^-3 in volume. The lattice constants a and c are given as a function of T. The transition temperature decreases monotonically with increasing x, and vanishes at x-- 0.08.