Structure and Stability of Multi-Component Amorphous Alloy Separated into Two Phases on Nanometer Scale for Hydrogen Strage.

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Large and small angle scattering experiments of (Ni_<1-y>Zr_y)_<1-x>V_x ternary and Y_<1-x>Al_x-D hydrogenated amorphous alloys have been studied by pulsed neutron scattering using accelator neutron sources.The chemical short range order parameters calculated from the first neighbor coordination numbers of Ni-Ni, Ni-Zr and Zr-Zr paircorrelations show positive and increase gradually with increasing Vcontent in (Ni_<1-y>Zr_y)_<1-x>V_x ternary amorphous alloy. This result means that the chemical ordering of Ni-Zr unlike atom pair correlation is enhanced by alloying V atom into Ni_<1-y>Zr_y binary system. The SANS intensity in the vicinity of Q-0.15 A^<-1> apart from that in Q<0.05 A^<-1> was newly observed in (Ni_<.67>Zr_<.33>)_<.7>V_<.33> ternary amorphous alloy, which is caused by the third element V atom. The characteristic function (r) obtained as the Fourier transform from the newly SANS intensity indicates that the concentration fluctuation with small size of about 9 A in diameter has been produced by the constituent V atom in (Ni_<.67>Zr_<.33>)_<.7>V_<.3> ternary amophous alloy. The atomic rearrangement, nano-scale fluctuation, induced by the third element may take place by the chemical frustration based on the chemical affinities among the constituent atoms.A1-Y amorphous alloys store D(H) atoms in the 6-fold octahedral site in low D(H) content and the 4-fold tetrahedral site in high D(H) content consisting of only Y atoms. Based on the observation of small angle neutron scattering intensity, it is concluded that the nanoscale concentration fluctuation of D atoms appears in A1-Y-D amorphous alloys.