Preparation and Characterization of Ultra-High-Purity Niobium

摘要: This paper presents a review of the efforts directed to preparation ultra-high-purity Nb published during last 15 years. The interest in high-purity has risen from need for materials high temperature and vacuum technology, superconductivity, solid state physics, its potential atomic energy fields. Depending on many applications, “purity” is understood different ways. Based results known purification processes (e.g., liquid-liquid extraction fluorides, distillation halogenides, electrolysis molten salts, electron beam float zone refining, electrotransport, degassing ultra vacuum), an optimized method been developed, consisting electrolytic refining which single crystals, melting, treatments. Material produced by process maximum impurity concentrations 10−l ppm Ta, 2×10−3 W, 4×10−6ppm Co, Fe, 10−5 Cr, etc., with less than 1 interstitials (C,N,O, except H) residual electrical resistivity ratio (RRR) >104. To accurately determine levels, improved analytical techniques were developed. Doping selected metallic (Cr,Mo,Hf,Ir) nonmetallic elements (C, 0) level served as both calibration effort tailor physical properties. General aspects development refractory metals, sources contamination purification, sample preparation, application Nb, well limiting bulk surface purity reactive metals are presented here.