Crystal structure of nanocrystalline Pr5Co19 compound and its hydrogen storage properties

Abstract The present study focuses on the structure and pressure-composition (P–C) isotherm measurements of nanocrystalline Pr5Co19 hydrides. The crystal structure and hydrogenation properties of Pr5Co19 are investigated by X-ray diffraction, refined using Rietveld method, and by transmission electron microscopy (TEM). This intermetallic compound crystallizes in the rhombohedral (3R) with Ce5Co19-type structure. The pressure-composition isotherm of Pr5Co19 was measured at room temperature. A single plateau was observed during the absorption-desorption process, the reversible hydrogen capacity reached 10 H/f.u (0.4 H/M). A peak broadening was observed in the X-ray diffraction (XRD) profile after hydrogenation, with no detection of any amorphous phase. The crystal structure of the Pr5Co19Hx hydrides has not been changed, it always conserves the rhombohedral structure (space group R 3 ¯ m ). The lattice parameters have increased with hydrogen content leading to an anisotropic expansion of the unit cell volume.