Residual Activity Method Research Articles

Diffusion of Sulfur in Selenium

AbstractMeasurements of sulfur diffusion have been carried out on single crystals and polycrystalline samples of the semiconductor element selenium using the residual activity method and a continuous surface method by means of the tracer S‐35 in the temperature range 40 to 95 °C. In the direction of the trigonal axis (‖ c) the volume diffusion in single crystals can be represented by D‖ = 1.1 × 10−5 exp (−0.6 eV/kT) cm2 s−1 and in the plane perpendicular to the trigonal axis (⟂ c) by D⟂ = 1.7 × 103 exp (− 1.15 eV/kT) cm2 s−1. Using the surface method the diffusion in polycrystalline material can be described by DP = 2.35 × 104 exp (− 1.20 eV/kT) cm2 s−1. The coefficient for the diffusion along short circuit paths is estimated to be in the region of 10−9 cm2 s−1. It can be presumed that S‐diffusion in both crystallographic directions of Se is governed by different mechanisms. The absorption of β‐radiation in Se can be expressed by the equation μ/ϱ = 26 E cm2 g−1.

Self‐Diffusion in Selenium

AbstractSelf‐diffusion measurements have been carried out in single crystals of the semiconductor element selenium using a residual activity method and Se‐75 as the tracer in the temperature range 152 to 215 °C. In the direction of the trigonal axis (| c‐axis) the data of the lattice diffusion can be represented by D⟂ = 0.2 exp (—1.2 eV/kT) cm2 s−1. The diffusion along the short circuit paths can be approximately described by the values Q≈︁ 0.5 eV and Q≈︁ 0.7 eV for the activation energy and by diffusion coefficients between 5 × 10−10 and 10−8 cm2 s−1 in the temperature range considered. The vacancy formation enthalpy in selenium is estimated to be about 0.75 eV. From the diffusion data determined the vacancy migration enthalpy is estimated to be about 0.5 eV along the c‐axis and 0.7 eV perpendicular to the c‐axis. It is possible to explain the self‐diffusion in selenium on the basis of a vacancy mechanism. The anomalous self‐diffusion behaviour of the elemental semiconductors and correlation considerations are discussed. Several typical features were found and the presented results for selenium are shown to be in agreement.

Diffusion of chromium and iron in Zircaloy-2

Using the residual activity method, the diffusion of chromium and iron in alpha and beta Zircaloy-2 has been studied in the temperature range of 650–1250 °C. The temperature dependence of their diffusivities (in cm 2/sec) can be described as D Cr/ α Zircaloy-2 (650–780 ° C) = 2.91 × 10 −6 exp (−35 620 cal/ RT), D Cr/ gb Zircaloy-2 (980–1250 ° C) = 6.31 × 10 −2 exp (−51 040 cal/ RT) and D Fe/ α Zircaloy-2 (650–780 ° C) = 2.56 × 10 −8 exp (−27 110 cal/ RT), D Fe/ β Zircaloy-2 (980–1250 ° C) = 1.03 × 10 −2 exp (−46 767 cal/ RT). A non-linearity in the Arrhenius plots has been observed in the phase transition region (780–960 °C). It has been explained on the basis of the statistical average of the diffusivity in both the phases present at a particular temperature in the transition region.

Diffusion of vanadium in aluminium and nickel

Diffusion studies of vanadium in aluminium and nickel were carried out using residual activity method. The diffusion coefficients (in cm 2/sec) are described as D V A1 = 6.05 × 10 −8 exp (−19,600/RT) D V Ni = 0.87 exp (−66,500/RT) The lower diffusivities associated with transition elements in aluminium are compared and discussed with the results of diffusion studies of the same elements in nickel.

The residual activity method for determining concentration distribution

The residual activity method for determining concentration distribution

Effect of a DC Field on the Lattice Diffusion of Silver‐110 in Copper and Gold

AbstractA study is made of the effect of a direct current, with a density of about 100 to 150 A/mm2, on the diffusion of silver‐110 in gold (99.99%) and copper (“high purity” grade) at temperatures above 800°C. Diffusion of silver‐110 is measured by the residual activity method. The direction of the electromigration and the magnitude of the activated ion “effective charge” is clear evidence for electron drag. The “effective charge” decreases linearly with temperature increase. The temperature coefficient of the “effective charge” of silver in gold and copper is higher than the temperature coefficient of the matrix conductivity.

The diffusion of iron in 3% silicon iron

Abstract The diffusion of 59Fe in a commercial 3% silicon iron alloy has been measured over the temperature range 967 to 1416°c by the residual activity method. The results are summarized by the equation: These results agree favourably with previous low temperature measurements made on an alloy of slightly different composition.

The diffusion of cobalt and iron in pure delta iron

The diffusion of Fe 59 and Co 60 in δ-Fe have been measured using a sectioning technique. The diffusion penetrations were determined by counting the radioactivity in the sections removed and also by the residual activity method. The results are summarized by the following equations: D Fe = 1.9 exp [−57.0 × 10 3/ RT], D Co = 5.5 exp [−61.2 × 10 3/ RT]. In both cases the activation energy and D 0 are significantly less than values previously reported for diffusion in the paramagnetic region of α-Fe. This amounts to approximately a threefold decrease in the value of D below that expected from extrapolation of the α-Fe data. The results indicate that were iron to retain the b.c.c. structure at all temperatures, the activation energy would demonstrate a non-linear functional dependence on temperature.

Photoneutron Cross Sections for Ag107, Mo92 and Zr90

Photoneutron cross sections and the yield curves were taken by the residual activity method for Ag 107 , Mo 92 and Zr 90 . Threshold energy were obtained as 9.35±0.1 MeV, 9.15±0.1 MeV, 12.38±0.1 MeV and 12.3±0.1 Mev for Ag 107,109 , Mo 92 and Zr 90 respectively. The energy for the maximum cross section was obtained as 14.5 MeV for Ag 107 , 16.5 MeV for Mo 92 and 17 MeV for Zr 90 . The giant resonance widths were measured about 5.3 MeV, 2.7 MeV and 2.9 MeV respectively. Intrinsic quadrupole moment determined from above data was (1.9±0.7)×10 -24 cm 2 for Ag 107 .

(γ, n) and (γ, 2n) reactions in93Nb

The (γ, n) cross-section of93Nb was measured by the residual activity method. Combining this result with the total neutron yield curve it was possible to separate the contributions of the (γ, n) and (γ, 2n) reactions. The ratio of these cross-sections was then compared with special attention to the 2.35 isomeric state (\(T_{\frac{1}{2}} = 13 hs\)) reported byJames; this activity was not found and we determined an upper limit for it as 0.02% of the 0.93 MeV line. An activity of 3.2% abundance due probably to γ rays of annihilation of positrons was found.

Effect of Noncollimated Radiation on Surface Activity Methods for the Determination of Diffusion Coefficients in Solids

The contributions of radiations arriving at a diffusion specimen surface, including angles other than 90°, have been evaluated for a number of counting geometries. Modifications are proposed for the Steigman, Shockley, and Nix equation for the surface activity method, the Gruzin equation for the residual activity method, and the Gatos and Kurtz equation for autoradiography on an oblique section through the diffusion zone. The theoretical equations for absorption of a divergent beam from a plane source as detected at a point counter have been shown to agree with experimental results for extended counters under not very restricted conditions. MnKα radiation from Fe55 was used to obtain a monochromatic source of X-rays.