Formation of RE_xNi_y (RE = La, Ce, Pr or ND) compounds by calciothermic reduction of La₂O₃, CeO₂, Pr₆O₁₁ and Nd₂O₃

LaNi₅, CeNi₅, PrNi₅ and NdNi₅ powders were prepared from the coorresponding oxides by a reduction-diffusion method using calcium as reductant and the morphology of the product and the mechanism of the reaction were examined. It was clarified that Ca_xNi_y compounds formed during the reaciton had a significant role in the formation of RE_xNi_y. Instead of a common direct reaction of xRE + yNi = RE_xNi_y, an indirect substitution reaction of aCa_xNi_y + bRE =cRE_xNi_y + dCa prevailed. This enhanced the rate of formation of RENi₅ significantly.