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  • Author or Editor: K. Kudo x
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Abstract  

The substoichiometric precipitation of fluoride with lanthanum was studied by using18F and140La tracers and it was found that fluoride could be precipitated substoichiometrically with lanthanum and the reaction ratio between fluoride and lanthanum was 3∶1. The pH range at which fluoride can be separated substoichiometrically with lanthanum is between 2 and 8. Barium and indium interfere in the precipitation of fluoride, sodium, copper and manganese, however, not. Fluorosilicate can also be precipitated substoichiometrically by using lanthanum as a precipitant and the reaction ratio between fluorosilicate and lanthanum was 1∶2. This separation was applied for the determination of oxygen in silicon crystals. The concentration of oxygen measured in some silicon crystals was between 5 and 27 ppm and in good agreement with those by non-destructive method and infrared spectrophotometry.

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Abstract  

The determination of trace elements in highly activated matrix components was carried out by neutron activation analysis using the radioisotope addition technique. The method is based on the addition to the irradiated test sample of a radioisotope which is a diffeent nuclide of the element to be determined. After separation, the chemical yield is calculated from the radioactivity added and the element is determined by an ordinary technique. Twelve elements in indium phosphide and eight elements in gallium arsenide could be determined by the method.

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Abstract  

The paper describes a method of radioactivation analysis for the determination of indium, copper and nickel. In the determination of indium, ordinary and displacement substoichiometries were applied for glassmaking materials while ordinary substoichiometry was applied for NBS standard reference materials. Copper and nickel in glassmaking materials and NBS standard reference materials were also determined by the displacement and ordinary substoichiometries. Indium contents in glassmaking materials by the two methods agreed with each other. The analytical results of indium, copper and nickel in NBS' SRM were also in good agreement with published values and certified values by NBS.

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Abstract  

Contamination sources of trace elements introduced into silicon crystals grown by the Czochralski technique are investigated: the signale comparator method in neutron activation analysis is applied to the determination of impurities in a silica crucible polycrystalline silicon, grown crystals and residual melt. When particular care is taken to avoid contamination during crystal growth, it is possible to obtain high purity silicon crystals in which impurity contents are almost below the detection limits of the analytical method.

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Abstract  

A method of rapid determination for indium, nickel and copper in Spinach (NBS; SRM-1570) by substoichiometric radioactivation analysis is described. The method is based on the principle that an equal amount of non-irradiated test sample is added to the irradiated standard sample and subsequent substoichiometric extraction for the irradiated test and standard samples is carried out. Indium is extracted as diethyldithiocarbamate into carbon tetrachloride, nickel as dimethylglyoximate into chloroform and copper as dithizonate into carbon tetrachloride. The radioactivities of these extracts are measured by NaI(Tl) or Ge(Li) detector coupled with pulse-height analyser. The analytical results obtained by the method were in good agreement with our published values and certified values by NBS.

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Abstract  

The single comparator method in neutron activation analysis has been applied to the investigation of the purity of silicon single-crystals of different origins. The following impurities were determined: Au, Sb, Co, Cu and Na. Studies were also carried out on the surface contamination of silicon samples introduced through steps of sample preparation and irradiation. Up to nineteen elements on the surface of samples were analysed and found to be easily reduced to low levels or detection limits by washing and etching.

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Abstract  

Substoichiometric isotope dilution analysis has been applied for the determination of trace elements in liquid samples, of carrier content in radioisotope solution and of concentration of organic reagent. Cu in mineral acids and in ZnSe single crystal was determined by the substoichiometric extraction with dithizone. The values of 1.8 and 0.018 ppm in nitric acid and distilled one and of 1.4 and 0.44 ppm in ZnSe were obtained. Cu and P carrier contents in64Cu and32P solutions were determined by the substoichiometric extractions with dithizone in CCl4 and with molybdic acid into MIBK in the series of the solutions adding various amounts of Cu or P carrier. An analogous method has been applied for the determination of dithizone and diethyldithiocarbamate solutions. The method was also applied for the determination of60Co radioactivity in environmental samples. The analytical result of water samples is described.

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Abstract  

Trace amounts of transition elements (Co, Cr, Cu, Fe, Mn and V) and other seven elements in optical waveguide samples were determined by INAA. The contents of impurities in ultra-pure materials are less than those of high-purity materials and of G.R. grade. The increase of contamination of trace transition elements and iridium from furnace or crucible are observed in the production of optical glass fibers. Up to seventeen elements were determined in five NBS biological standard reference materials: Oyster Tissue: SRM-1566, Brewers Yeast: SRM-1569, Spinach: SRM-1570, Orchard Leaves: SRM-1571 and Tuna Fish, and in four Japanese biological standard reference materials: Tea Leaves B&C, Pepperbush and Shark Meat. The analytical results in NBS and Japanese standard reference materials are in good agreement with published values and certified values by NBS.

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Abstract  

A method of radioactivation analysis has been developed for the determination of Mn, Cu, Zn and Cd impurities in gallium arsenide. After irradiation, arsenic and gallium are separated by distillation and solvent extraction, then the impurity elements are determined by substoichiometric methods. Mn is extracted as tetraphenylarsonium permanganate into chloroform, and other elements as dithizonates in carbon tetrachloride under various conditions. The contents of Mn, Cu, Zn and Cd in a gallium arsenide crystal with a carrier concentration of 1.8·1016/cc were 0.004, 0.02, 0.006 and 0.04 ppm, respectively.

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Résumé  

Depuis qu'une nouvelle méthode d'analyse par activation basée sur la substoechiométrie a été proposée, un certain nombre de techniques ont été développées pour rechercher les éléments à l'état de trace. La nouvelle technique se décompose en (1) la méthode directe, (2) la méthode du traceur en quantité variable, (3) la méthode par comparaison. Ces méthodes ont les avantages suivants: la correction du rendement chimique n'est pas nécessaire, les réactions nucléaires secondaires et l'autoabsorption ne constituent pas des causes d'erreur dans le dosage. On décrit le principe de ces métho des et la détermination d'éléments à de très faibles concentrations dans les matériaux de haute pureté par les méthodes (2) et (3).

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