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Abstract  

The substoichiometric determination of some impurities in gallium arsenide and selenium supplied by OEC and IUPAC, respectively, as reference materials for radioactivation analysis is described.

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Abstract  

A method of radioactivation analysis has been developed for the determination of indium and tin. It is based on substoichiometric extraction of indium diethyldithiocarbamate into carbon tetrachloride from a slightly ammoniacal solution in the presence of potassium cyanide. With this method, indium can be determined via116m In (T=54 min) and tin via113m In (T=104 min) which is formed by the reaction112Sn(n, ψ)113Sn. The method has been applied to the determination of indium in metallic zinc and of tin in tin-doped gallium arsenide, and 0.4 ppb of indium was analyzed in a zinc sample.

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Abstract  

A simplified method for the substoichiometric analysis of phosphorus has been developed and applied to determine the concentration distribution of phosphorus in the region of a SiO2–Si interface in order to explain why phosphorus is lost from the ion-implanted silicon surface throughout the oxidation and oxide removal processes. It is revealed that phosphorus piles up on the SiO2 side at the interface by the thermal oxidation of silicon surface and is removed with the oxide by wet etching and with the resulting silicon by RCA cleaning. This results in a total loss of ion-implanted phosphorus of 3.5%.

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Abstract  

A method of radioactivation analysis has been developed for the substoichiometric determination of cobalt, copper and manganese in glass and glass-making materials. The substoichiometric extraction of cobalt with α-nitroso-β-naphthol was studied and simple procedures are suggested for the determination of the three elements. Cobalt is extracted substoichiometrically as α-nitroso-β-naphtholate into chloroform from solution of pH 6.2, copper as dithizonate in carbon tetrachloride from weak acidic solution, and manganese as tetraphenylarsonium permanganate into chloroform after oxidation to permanganate. Contents from 2 ppm to 3 ppb of cobalt, copper and managanese were analysed in glass-making materials, and it is shown that the method for their determination is reliable and superior in accuracy and reproducibility.

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Abstract  

The paper deseribes the determination of indium in metallic tin and cadmium metals by the direct method, which is a variant of substoichiometric radioactivation analysis. It is based on substoichiometric extraction of indium diethyldithiocarbamate into carbon tetrachloride. Indium in tin metal was determined by116mIn (T=54 min), while115mIn (T=4.5 h), formed by the reaction114Cd(n, γ)115Cd was used for cadmium samples. The irradiated sample was dissolved and the radioactivity of116mIn or115mIn, A, was measured. After the separation of indium from the matrix, a known amount of indium, m, was separated substoichiometrically and the radioactivity, a, was measured. Indium was calculated as Mx=m A/a. If a known amount of the element, M, is added to the irradiated sample in advance, the equation for calculation is given as Mx-m A/a−M. By this method, indium can be determined without any consideration of self-shielding and secondary nuclear reaction of the matrix.

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Abstract  

Uranium and thorium in LSI materials were determined by INAA and α-particles in these materials were also measured. The contents of uranium and thorium and the α-activity in ceramics and zirconia samples were very high. Calculation of α-flux from uranium and thorium contents and analysis of α-spectra were carried out for the ceramics and zirconia samples. The calculated values of α-flux in these samples agreed with the α-flux measured.

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Abstract  

The surface concentrations of copper and iron in currently used silicon wafers are lower than 1014 atoms·m–2. To determine such ultra-trace elements accurately by neutron activation analysis, we measured the efficiencies of a well-type Ge detector for59Fe -rays and64Cu annihilation -rays. We also developed methods for preparing samples for copper and iron analysis including a low-temperature silicon direct-bonding technique. We have applied these techniques to determine copper and iron on the surface of clean silicon wafers, and obtained concentrations of 1013–1014 atoms·m–2.

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Abstract  

A substoichiometric analytical method, using a carrier-free radioisotope, is developed for the accurate and precise determination of yttrium. The method is applied to yttrium determination in high-Tc superconducting oxide ceramics. The error of the analytical results is estimated to be within 1%.

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Abstract  

Carrier-free88Y radioisotope, which has the longest half life /T=106.6 d/ of yttrium radioisotopes and is a -ray emitter, was obtained by proton irradiation of strontium, followed by cooling for one month. Then,88Y was purified by precipitating strontium as strontium nitrate and extracting yttrium with tri-n-butyl phosphate /TBP/. The decontamination factor of strontium to yttrium was more than 4×103 and chemically pure yttrium radioisotope was obtained.

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Journal of Thermal Analysis and Calorimetry
Authors:
Y. Akishige
,
H. Shigematsu
,
T. Tojo
,
H. Kawaji
, and
T. Atake

Summary Specific heats on the single crystals of Sr2Nb2O7, Sr2Ta2O7 and (Sr1-xBax)2Nb2O7 were measured in a wide temperature range of 2-600 K. Heat anomalies of a λ-type were observed at the incommensurate phase transition of T INC (=495 K) on Sr2Nb2O7 and at the super-lattice phase transition of T SL (=443 K) on Sr2Ta2O7; the transition enthalpies and the transition entropies were estimated. Furthermore, a small heat anomaly was observed at the low temperature ferroelectric phase transition of T LOW (=95 K) on Sr2Nb2O7. The transition temperature T LOW decreases with increasing Ba content x and it vanishes for samples of x>2%.

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