Patent ID: 7005212

Claim:
A hydrogen absorbing alloy containing as a principal phase at least one phase selected from the group consisting of a second phase having a rhombohedral crystal structure and a first phase having a crystal structure of a hexagonal system excluding a phase having a CaCu 5 type structure, wherein a content of a phase having a crystal structure of AB 2 type is not higher than 10% by volume including 0% by volume in the hydrogen absorbing alloy, a parallel growth region precipitates in at least one crystal grain of the principal phase and has a crystal structure differing from a crystal structure of the principal phase, and the hydrogen absorbing alloy has a composition represented by general formula (1) given below: R 1-a-b Mg a T b Ni Z-X-Y-α M1 X M2 Y Mn α (1) where R is at least one element selected from rare earth elements, said rare earth elements including Y, T is at least one element selected from the group consisting of Ca, Ti, Zr and Hf, M1 is at least one element selected from the group consisting of Co and Fe, M2 is at least one element selected from the group consisting of Al, Ga, Zn, Sn, Cu, Si, B, Nb, W, Mo, V, Cr, Ta, Li, P and S, the atomic ratios of a, b, X, Y, α and z are respectively satisfy conditions of: 0.15≦a≦0.37, 0≦b≦0.1, 0.53≦(1-a-b)≦0.85, 0≦X≦1.3, 0≦Y≦0.5, 0≦α<0.135 and 3≦Z≦4.2.