A侧元素对AB_3型贮氢合金晶体结构的影响

Effect of A-Side Element on Crystal Structure of AB_3-Type Hydrogen Storage Alloy

以AB3型贮氢合金中的LaNi3合金为参考相,选取CeNi3、LaY2Ni9和CeY2Ni93种合金为研究对象,运用X射线衍射技术结合Rietveld结构精修的方法,研究了A侧元素对AB3型贮氢合金晶体结构的影响。研究表明,LaNi3、LaY2Ni9和CeY2Ni9的晶体结构均与PuNi3型结构相吻合,具有R-3m的空间点群,而CeNi3的空间点群则为P63/mmc。与LaNi3相比,LaY2Ni9合金的点阵常数a和c分别减小了0.7%和2.0%,晶胞体积减小了3.3%;与CeY2Ni9相比,LaY2Ni9合金的点阵常数a减小了0.9%,c增加了0.7%,晶胞体积减小了1.2%。A侧原子的点阵位置具有选择性,即原子半径大的原子倾向于占据点阵中3a位置,半径小的原子倾向于占据6c位置。

As the representive for AB3-type intermetallics, CeNi3, LaY2Ni9 and CeY2Nig, have been studied and compared with LaNi3. The effect of A-side element on crystal structure of AB3-type compounds was investigated by means of X-ray diffraction and Rietveld structure refinement. The results indicate that LaNi3, LaY2Ni9 and CeY2Ni9 adopt a rhombohedral structure of PuNi3-type （R-3m space group）, while the space group of CeNi3 is P63/mmc. As compared to LaNi3, LaY2Ni9 shows isotropic variations in the cell parameters, with the decrease of 0.7% in α, and 2.0% in c, which leads to the cell volume reduction of 3.3%. Compared to CeY2Nig, LaY2Ni9 shows a decrease of 0.9% in α, and the increase of 2.0% in c, and an overall cell volume reduction of 1.2%. Among the two available crystallographic sites for A-side atom, the atom with a larger radius occupies the site 3α preferentially and the smaller one occupies the site 6c in the lattice.