Purification of Rare Earth Metals by Advanced Electron Beam Floating Zone Melting Method

本文采用传统的高真空电子束浮动区熔炼技术和两种新型的先进电子束浮动区熔炼技术，研究了钕、镧的提纯、非金属和金属杂质的去除。在后者的情况下，EBFZM处理分别在低压氢气（P_<H2大气压=10^<-3>至10^<-5> Pa）和样品棒上叠加直流电流（500至1000 a /cm^2）下进行。常规EBFZM处理后，碳和硫的含量由于带过引起的分布而降低，而钕和镧的氧和氮含量几乎没有下降。蒸气压高于钕和镧的金属杂质，如钙和镁，可以通过汽化去除。虽然铁、硅和铜不可能通过汽化还原，但它们可以在区域通过时重新分布。经EBFZM处理后，钕、镧的残余电阻率均因各自杂质的减少而增大。另一方面，先进的EBFZM技术有望比传统的EBFZM技术更有效地从Nd和La中还原非金属杂质。但是，为了充分利用EBFZM对稀土金属的净化效果，首先要研究和找出EBFZM先进处理的稳定区熔化的良好条件。

Purification of neodymium and lanthanum, removal of non-metallic and metallic impurifies from their rods, has been examined by the conventional electron beam floating zone melting (EBFZM) technique in a high vacuum and furthermore by two types of the novel advanced EBFZM techniques. In case of the latter, EBFZM treatments have been done in the atmosphore of low pressure of hydrogen (P_<H2>=10^<-3> to 10^<-5> Pa) and with a superimposed DC electric current (500 to 1000 A/cm^2) on the sample rods, respectively.After the conventional EBFZM treatment, carbon and sulfur contents are found to be reduced by their distribution caused by the zone pass, while the reduction of exygen and nitrogen contents are scarcely observed for neodymium and lanthanum. Metallic impurities having vapor pressures higher than neodymium and lanthanum, such as calcium and magnesium, can be removed through the vaporization. While the reduction of iron, sillicon and copper are not possible through vaporization, but they can be redistributed during zone passes. The residual resistivity ratios of neodymium and lanthanum increased after the EBFZM as a result of the decrease of respective impurities.On the other hand, the advanced EBFZM techniques are expected to be more effective for reduction of non-metallic impurities from Nd and La than the conventional one. However it is recognized that we should, first of all, investigate and find out the good conditions for the stable zone melting on the advanced EBFZM treatment, to utilize the purification effect of it on rare earth metals.