| 摘要 |
PURPOSE:To improve the battery characteristics of a nickel hydrogen secondary battery by specifying the network segregation state in a rare earth - nickel hydrogen storage alloy where the grain size and content of a crystal are regulated to specific values, respectively. CONSTITUTION:This ingot is a rare earth-nickel alloy ingot containing a crystal having a grain size of 1-50mum in a minor axis direction and 1-100mum in a major axis direction by >=90vol.%, preferably >=95vol.%. It is preferable that, in particular, the segregation of component elements in a main-phase crystalline grain is regulated to <5wt.% and also the spacing of network segregation part is regulated to 1-40mum. Further, it is preferable to regulate the thickness of the hydrogen storage alloy ingot to 0.1-20mm. This ingot can be produced by uniformly solidifying a molten rare earth - nickel alloy under the cooling conditions of 10-1000 deg.C/sec cooling rate and 10-500 deg.C degree of supercooling.
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