Development of sample holder for in situ neutron measurement of hydrogen absorbing alloy

We developed a sample holder for in situ measurement of hydrogen absorbing alloy. In order to prevent the hydrogen absorption by vanadium, copper is coated with 2 μm thickness on inner surface of the vanadium holder. The effect of copper coating and the performance of the holder were evaluated by neutron diffraction and PDF profiles. The lattice parameters a and c of La2Ni7 with Ce2Ni7-type structure were refined as 0.505921(4) and 2.468608(4) nm by Rietveld analysis. The Cu–Cu correlation peak around r = 0.255 nm was not observed in the PDF profile. Thus the holder is useful for in situ measurement of hydrogen absorbing alloy. The diffraction and PDF profiles of La2Ni7Dx (0 < x < 10.5) were collected using a deuterium pressure of 3.7 MPa, and the changes of crystal and local structures were clearly observed.

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► The profiles of the alloy phase, La2Ni7D5.6 and La2Ni7D10.5 are different to each other.
► The phase transition of La2Ni7 during the deuteration is clearly observed.