On the Debye temperature in sigma-phase Fe–V alloys

A series of σ-phase Fe100−xVx samples with 34.4 ≤ x ≤ 59.0 were investigated by neutron and X-ray diffraction and Mössbauer spectroscopy (MS) techniques. The first two methods were used for verification of the transformation from α to σ phase and they also permitted to determine lattice parameters of the unit cell. With MS the Debye temperature, ΘD, was evaluated from the temperature dependence of the centre shift, <CS>, assuming its entire temperature dependence originates from the second-order Doppler shift. To our best knowledge, it is the first ever-reported study on ΘD in σ-FeV alloys. Both lattice parameters i.e. a and c were revealed to linearly increase with x. ΘD shows, however, a non-monotonic behaviour as a function of composition with its extreme values between ∼425 K for x ≈ 40 and ∼600 K for x ≈ 60. A local maximum of ∼525 K was found to exist at x ≈ 43.