Control of hydrogen storage properties of (La,Ce,Nd,Pr)(Ni,Co,Mn,Al)5 alloys with microstructural parameters

• Hydrogen storage properties can be varied by changing the crystal lattice volume.
• Crystal lattice volume is related with molar ratios of the elements.
• Atomic radius factor is defined by atomic radii and molar ratios of each element.
• Hydrogen storage properties can be controlled using the atomic radius factor.
• Low-cost alloys (Nd-free/Ce-rich) can be prepared using the atomic radius factor.

Atomic radius factor—a factor related to the composition in (La,Ce,Nd,Pr)(Ni,Co,Mn,Al)5 alloys, was deduced and used to prepare low-cost alloys. The plateau pressure and hydrogen storage capacity were changed with respect to the crystal lattice volume of the (La,Ce,Nd,Pr)(Ni,Co,Mn,Al)5, which could be controlled by changing the ratio of the elements in the alloy. Therefore, the plateau pressure and hydrogen storage capacity were adjusted by using the atomic radius factor, defined as the summation of the multiplication of the atomic radii and molar ratios of each element in the alloy. Finally, low-cost alloys (Nd-free/Ce-rich) were designed and prepared using the atomic radius factor. By simultaneously increasing the amounts of Ce and Mn in the alloy, the atomic radius factor and the crystal lattice volume of the alloy could be made similar to those of a commercial alloy. Consequently, it is possible to control the hydrogen storage properties and to prepare low-cost alloys with hydrogen storage properties similar to those of commercial alloy using the atomic radius factor.