Hiroaki Hoshikawa

Purification of 6N Aluminum by Ultrahigh Vacuum Melting

In order to improve the purity of 6N aluminum, it was melted in a vacuum of 3-6×10−6 Pa for 30 min and solidified gradually. The melted samples were cut into several pieces and the residual impurities of each part were analyzed by Glow Discharge Mass Spectrometry (GDMS). The Residual Resistivity Ratio (RRR) of each part was measured and the relationship of RRR with residual impurities is discussed. The purity of the melted sample was improved in comparison with that of the raw material, and the measured RRR almost doubled to 40000. GDMS analysis revealed that the amounts of elements of partition coefficient k 1 were not reduced. While each impurity concentration ratio in this study is about one-tenth of that in the previous report, the purification efficiency of each element in this study and that in the previous report matched well. Although the estimated RRR values from composition analyses were larger than the measured RRR values, both showed similar tendencies with regard to specimen position and also corresponded well with regard to impurity distribution.