Pressure dependence of hydrogen-induced amorphization in C15 Laves phase ErFe2

Process and mechanism of hydrogen-induced amorphization in C15 Laves phases RFe2

“…The relation between T p and the hydrogen pressure for ErFe 2 is similar to that for DyFe 2 [19]. That is, T p for hydrogen absorption, HIA and the decomposition of a-ErFe 2 H x into α-Fe + ErH 3 show a negative pressure dependence, butT p for the precipitation of BiF 3 -ype ErH 3 shows a positive one.…”

“…HIA is closely related to the disproportionation reaction that dominates a lifetime of hydrogen storage alloys, so that it is important to make clear the controlling factors of HIA. HIA has been observed in the intermetallic compounds A x B 1−x consisting of hydride forming (A) and non-hydride forming metals (B) with the crystal structures such as C15, B8 2 , C23, D0 19 and L1 2 [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Among these, structural changes in the C15 Laves phases RFe 2 (R = rare earth metals) are particularly interesting, because both a crystalline and an amorphous hydride form depending on the hydrogenation temperature [12].…”

“…That is, hydrogen absorption, HIA, the precipitation of RH 3 and the decomposition of the remaining amorphous phase occur in RFe 2 (R = Sm, Gd, Tb, Dy and Ho). On the contrary, hydrogen absorption and HIA occur simultaneously in CeFe 2 [18], while HIA and precipitation of ErH 3 do simultaneously in ErFe 2 [15]. However, the mechanism of HIA in the C15 Laves phases is still uncertain.…”

Pressure Dependence of Hydrogen-Induced Transformations in C15 Laves Phase DyCo<SUB>2</SUB>

“…It has been reported that crystalline hydrides c-RM 2 H x can desorb hydrogen in the crystalline state and their Ar-DSC curves show only endothermic peaks at relatively low temperatures without exception. 14,15,18,19) The Ar-DSC curve of DyCo 2 heated to above the first The sample heated to above the first exothermic peak (to 400 K) (a,b), the second peak (to 623 K) (c), the third peak (to 723 K) (d) and to the fourth peak (to 798 K) (e).…”

“…Furthermore, T p of HIA for C15 Laves RFe 2 (R ¼ Tb, Er) shows also a same strong negative pressure dependence. [15][16][17][18] It has been proposed that HIA of C15 Laves RM 2 occurs by the short-range diffusion of R and M atoms. Therefore, it is interesting to compare the pressure dependence of HIA for DyCo 2 with that for DyFe 2 .…”