THE EFFECT OF NB ON PHONONS OF SUPERCONDUCTORS C-15V2ZR AND V2(HFZR)

Inelastic neutron scattering spectra from superconducting material C-15 V2Zr, V2Zr0.95Nb0.05 and V2Hf0.5Zr0.5,V2Hf0.5Zr0.3Nb0.2 were measured by neutron time-of-flight method. It was found that the additional content of Nb influenced the superconducting transition temperature Tc and phonon frequencies of V2Zr1-xNbx in a way different from that of V2Hf0.5Zr0.5-xNbx. The Tc increases and the phonon frequencies "soften" with increasing x for the former, while the Tc slightly decreases and the phonon frequencies "harden" for the latter. The result that the phonon frequencies of V2Zr0.95Nb0.05 are softer than that of V2Zr is somewhat in contradiction with the previous results, which show that the magnetic susceptibilities decrease and the geometric mean phonon frequencies increase. The result that the phonon frequencies of V2Hf0.5Zr0.3Nb0.2 are harder than that of V2Hf0.5Zr0.5 can be considered as the result of hybridization of conduction band, which is studied for close-packed compounds by means of LMTO (linear combination of muffin-tin orbitals) method.