A method of further purification of zone-refined aluminum by cold-crucible levitation melting in ultra-high vacuum

We have found that impurity elements with a solid/liquid distribution coefficient k less than unit are removed efficiently by levitation melting in ultra-high vacuum. Therefore, this method was applied to the purification of the tail part of zone-refined aluminum, because in this part the impurity elements with k less than unit are accumulated. The tail part of zone- refined aluminum with residual resistance ratio RRR = R (300K)/ R (4. 2K) = 1 500 to 15 000, was melted in ultra-high vacuum (about 10–8 Pa) in a cold crucible induction furnace. By this way, the RRR of the sample was improved to 20000