Purification of 6N Aluminum by Ultrahigh-Vacuum Melting

Abstract

To improve the purity of 6N-grade aluminum, it was melted in a vacuum of 3­6 © 10 ¹6 Pa for 30min and solidified gradually. The melted samples were cut into several pieces and the residual impurities of each portion were analyzed by glow discharge mass spectrometry (GDMS). The residual resistivity ratio (RRR) of each portion was also measured and the relationship between RRR and residual impurities was investigated. The purity of the melted sample was improved in comparison with that of the raw material, and the measured RRR was almost doubled to 40000. GDMS analysis revealed that the concentration of the elements with partition coefficient k 1 was not reduced. While each impurity concentration ratio in this study is about one-tenth of that in our previous report, the purification efficiency of each element in this study and that in the previous report were in good agreement. Although the values of RRR estimated from composition analysis were larger than the measured RRR values, both exhibited similar tendencies with regard to the specimen position and also corresponded well with impurity distribution. [doi:10.2320/matertrans.M2012041]