Phase transformation and lattice-strain formation in Ti_1.0v _1.1Mn_0.9during first absorption and desorption

We used powder X-ray diffraction (XRD) and Rietveld refinement to study phase transformation and the lattice strain introduced into each hydride phase of Ti_1.0V_1.1Mn_0.9 during first absorption and desorption. Hydrogénation proceeded from a solid-solution phase to a dihydride phase via a monohydride phase. Each single-phase region was observed beside two clear plateau regions on the pressure-composition (P-C) isotherm. In contrast, the desorption P-C isotherm showed only one clear plateau, corresponding to a two-phase region of the dihydride and the monohydride. The plateau was connected to a two-phase region of the monohydride and a solid-solution phase, and to another region of solidsolution phases. The monohydride single-phase region was not clearly observed during desorption. Isotropic lattice strain was introduced, and increased with phase transformation during the first absorption. The strain increased further in the subsequent phase transformation during desorption, particularly upon formation of a solid-solution phase.