Metallurgical state of lanthanum and its effects on the activation behaviour of Zr(Cr0.4Ni0.6)(2) hydride formation

Lanthanum was added to cubic C15 type Zr(Cr0.4Ni0.6)(2) to prepare Zr(Cr0.4Ni0.6)(2)La-0.05. Metallographical observation and microprobe analysis indicate that lanthanum does not dissolve in the Laves phase, but preferentially combines with nickel to form the LaNi phase which precipitates dispersively at the grain boundaries of the Laves phase together with Zr7Ni10. It is found by X-ray diffraction that the cell parameters of the Laves phase before and after adding lanthanum are the same. However, Zr(Cr0.4Ni0.6)(2)La-0.05 shows much better activation behaviour than Zr(Cr0.4Ni0.6)(2), both in solid-H-2 reaction and alkaline electrolyte, which is believed to result from the presence of the LaNi phase.