Formation of a tetragonal phase hydride in Ti–Mo–H system

Crystal structure of the tetragonal ɛ-phase deuteride of Ti–15at%Mo alloy determined by neutron diffraction

“…On the other hand, as shown in Fig. 3, the complementary XRD data appear to be consistent with our previous XRD results [7], where no remnant fcc ␦-phase is presented. The reason is that the position of the strongest (1 1 1) reflection of the remnant ␦-phase in XRD coincides Table 1 The crystal structural information of the -phase deuteride derived from the Rietveld refinement.…”

“…As illustrated in Table 1, the differences of the D concentrations and lattice parameters of the two -phase cells derived from the fit indicate that the -phase exists in a relatively broad range of D concentrations, which is consist with our previous conclusion that such tetragonal hydride can form between the ratio of H/M = 1.1-1.7 in the Ti-Mo-H system [7]. As the deuteride has a considerably lower D concentration than that of the -phase in Ti-H(D) system, its lattice parameters are accordingly reduced.…”

“…Then certain amount of deuterium was drawn out of the deuteride by gradually reducing the pressure in the hydrogenator at the temperature of ∼380 • C, until D concentration in the sample reach a level of D/M = 1.56 (3). According to previous work, the tetragonal deuteride should be formed under this situation [7].…”

“…In the previous XRD study [7], a new body-centered tetragonal (bct) hydride (denoted as -phase by us) of the Ti-Mo alloy with Mo contents of 10-15 at% was observed in the unsaturated hydride samples. The H concentration of the hydride is between that of the -phase and ␥-phase in Ti-H system, and has c/a axial ratio of corresponding face center tetragonal (fct) unit cell similar to that of the -phase but different from that of the ␥-phase.…”

“…The crystal structure and H occupancy of the ␦-phase hydride of the Ti-Mo alloy has been investigated using neutron and XRD techniques [4,5]. The in situ and ex situ XRD studies on the thermal stability and phase transformation of the hydrides have indicated that different phases of similar H concentration can be formed at different temperature regions during the dehydrogenation process [6,7].…”