Hydrogen storage in high-entropy alloys with varying degree of local lattice strain

We have investigated the structure and hydrogen storage properties of a series of Ti, V, Zr, Nb and Ta based high-entropy alloys (HEAs) with varying degree of local lattice strain by means of synchrotron radiation powder X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry and manometric measurements in a Sieverts apparatus. The obtained alloys have body-centred cubic (bcc) crystal structures and form face-centred cubic (fcc) metal hydrides with hydrogen-to-metal ratios close to 2. No correlation between the hydrogen storage capacity and the local lattice strain is observed in this work. Both bcc and fcc unit cells expand linearly with the zirconium-to-metal ratio [Zr]/[M], and increased concentration of Zr stabilizes the hydrides. When heated, the hydrides decompose into the original bcc alloys if [Zr]/[M]