Deuteron and Niobium‐93 Magnetic Resonance Study of Niobium Deuterides

Abstract

AbstractNiobium deuterides in the composition range NbD0.55–NbD0.88 were investigated by means of deuteron and 93Nb magnetic resonance over the temperature range 4.2–420 K. The β‐α transition, in the temperature range 340–415 K for these compounds, is sharply defined by the extinction of the deuteron quadrupole interaction as well as by the appearance of the central component of the 93Nb spectrum when the cubic α phase is formed. These results are discussed in relation to other determinations of the β‐α transition temperature. No other significant changes in the deuteron magnetic resonance spectrum are observed, down to 4.2 K, at which temperature the quadrupole coupling constants are essentially equal, with an average value, e2qQ/h = 33.0 kHz. The temperature dependent behavior of the 93Nb resonance spectrum indicates that the boundary between the α + β and β regions of the Nb  H(D) phase diagram must pass between the compositions NbD0.78 and NbD0.82 at 300 K. The NMR observations do not furnish positive support for the occurrence of the ζ and ϵ phases nor for the occurrence of the cubic γ phase, but they are not incompatible with the occurrence of these phases. These observations may reflect an intrinsic insensitivity of the deuteron quadrupole interaction to long range ordering of the deuterium in the lattice. Measurements of the 93Nb Knight shift are in close agreement with the shifts obtained in Nb  Mo and Nb  Tc alloys, and suggest that up to this relatively high deuterium content (D/Nb = 0.88) the deuterium continues to yield its electron to the conduction band of the metal.