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Abstract

Pure alkali metal preparation is a complex problem: in most available commercial samples, all of them are simultaneously present. Conventional separation techniques are not always effective enough to reach parts per million total impurity levels. However, near the melting point, superficial segregation occurs. A zone melting derived technique coupled with a specifically developed solvent extraction process allows the total impurity content of sodium to be lowered below a few parts per million. The described thermal process, although using chemical reactions, is purely physically steered: it purifies as well potassium containing sodium as sodium containing potassium. 4 alkali metals are considered: Li, Na; K, and Cs.

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Abstract  

Argon ion induced X-ray emission has been used for analysis of Si and Cl present at low concentrations in CdTe crystals. The influence of zone melting on the distribution of these elements along the crystal is examined.

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Abstract  

A new chemical separation procedure for the determination of silicon in iron after neutron activation was developed. It uses two separation steps, one on a cation exchange resin in HCl−HF-acetone medium, and the other on alumina at pH 9. The detection limit for silicon was 0.02 μg. This analytical procedure was applied to the control of the zone-melting purification of iron.

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Abstract  

We have developed charged particle activation analysis to determine light elements at a sub-ppb level. This analytical method is characterized by sample bombardment with charged particles at a few tens of mA and substoichiometric separation for13N,11C and18F within two half-life times and with decontamination factors of more than 108. Nuclear reactor interference is also estimated with this method. This analytical method is confirmed to be useful for characterizing highly purified materials from analytical results for boron, carbon, nitrogen and oxygen in Nb refined by the floating zone melting method.

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Abstract  

Convenient processes are described for the charged particle activation analysis for carbon, nitrogen, and oxygen in semiconductor silicon. Suitable activation reactions and incident particle energies were selected, and the interferences examined; the activation curves for the Si+3He→11C and Si+3He→18F reactions, which may seriously interfere with3He activation analysis, were measured, and the interference caused by the fission of the matrix itself is discussed. A simple technique for the separation of11C present in silicon is proposed. Reliable determination of as low as several parts per billion of the three elements has thus become possible. Semiconductor silicons of various origin were analyzed for C, N and O, and the behaviour of these elements during zone-melting is reported.

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