Time-of-Flight Pulsed Neutron Diffraction of Pd_<0.8>-Si_<0.2> Amorphous Alloy Using the Electron Linac

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The structure factor S(Q) of Pd_<0.8>-Si_<0.2> amorphous alloy was measured over wide range of Q (=4π sin θ/λ) up to 40 A^<-1> by time-of-flight neutron diffraction using pulsed epithermal-neutron generated from the Tohoku University electron linac. The S(Q) has definitely shown an oscillation even in range of Q〓25 A^<-1>. The 1st peak of the pair distribution function Fourier transformed from the S(Q) has been split into two sub-peaks at the position of 2.42 and 2.81 A. Combining the neutron result with the X-ray result, the 1st sub-peak was verified to correspond to Pd-Si pair and the 2nd sub-peak the mixture of Pd-Pd pair and Pd-Si pair where Pd atom was substituted with Si atom. The average numbers of the nearest neighbour atoms around the Pd atom at origin are 1.7 Si atoms in the 1st sub-peak and 10.7 Pd and 1.5 Si atoms in the 2nd sub-peak. There may be no Si-Si pair with the nearest interatomic distance in the alloy. Such a relation for atom-atom pairs is found in the crystalline Pd_3Si compound, too. The liquid structure of the alloy was also measured and concluded to be essentially close to the amorphous structure except more blurring of peaks.
東北大学の論文