Preparation of High-Purity Nickel

Nickel single crystals have been prepared by electron beam float zone melting with resistance ratios of 4000. These ratios were obtained by the selective removal of carbon by an oxygen treatment during the zone melting of specially prepared electrolytic nickel. Our data suggest that carbon and iron have a nearly equal contribution to the residual resistivity of . Thus, the total carbon and iron content of nickel, neglecting all other contributions to the residual resistance, must be less than 5 atom ppm to obtain a 4000 resistance ratio. Several commercial sources of nickel were zone melted and found to contain too much iron to approach this purity level.