Precise Purity Evaluation of High-Purity Metals by Residual Resistivity Ratio

点击翻译按钮获取中文摘要

For purification of metals, the evaluation of the purified metals should be an important subject. So the residual resistivity ratio (RRR = ρィイD2298KィエD2/ρィイD24.2KィエD2) has been widely used to estimate the purity of high-purity metals. However, to evaluate the metal-purity with high accuracy by RRR, there are some problems to be considered.In this work, the residual resistivity ratios for several high-purity metals, such as Cu, Fe, Co and Cr, prepared by the various purification processes have been measured and the influence of the annealing condition, the size effect, the purity and the remaining trace impurities of the measured specimens on the RRR values has been examined, respectively. The main results are follows.(1) The optimum annealing conditions of the specimen wire before the RRR measurement have been studied and the most suitable annealing temperature and period were determined for high-purity Cu, Fe, Co and Cr, respectively.(2) For the size effect of RRR on high-purity Cu, the relationship between RRRィイD2WィエD2 measured for the wires, RRRィイD2BィエD2 of the bulk copper and the specimen diameter has been determined. The RRRィイD2WィエD2 is found to be dependent largely on the specimen diameter. Then, the influence of the size effect must be considered carefully whenever to evaluate and to compare the purity of the high-purity metals by RRR.(3) The increasing tendencies of the RRR values with raising in the specimen purity in the range of 99.9% to above 99.999% have been made clear for Cu, Fe and Co.(4) Dependence of the RRR on the concentration of some trace impurities, like phosphorous in high-purity Fe, has been determined quantitatively.