[en] Ion implantation can be used to alter in the optical response of insulators through the formation of embedded nano-sized particles. Single crystal alumina has been implanted at ambient temperature with 50 keV Ca⁺ to a fluence of 5 x 10¹⁶ ions/cm². Ion channeling, Knoop microhardness measurements, and transmission electron microscopy (TEM) indicate that the alumina surface layer was amorphized by the implant. TEM also revealed nano-sized crystals ∼7--8 nm in diameter. These nanocrystals are randomly oriented, and exhibit a face-centered cubic structure (FCC) with a lattice parameter of 0.409 nm ± 0.002 nm. The similarity between this crystallography and that of pure aluminum suggests that they are metallic aluminum nanocrystals with a slightly dilated lattice parameter, possibly due to the incorporation of a small amount of calcium. Energy-filtered transmission electron microscopy (EFTEM) provides an avenue by which to confirm the metallic nature of the aluminum involved in the nanocrystals. EFTEM has confirmed that the aluminum present in the particles is metallic in nature, that the particles are oxygen deficient in comparison with the matrix material and that the particles are deficient in calcium, and therefore not likely to be calcia. The particles thus appear to be FCC Al (possibly alloyed with a few percent Ca) with a lattice parameter of 0.409nm. A similar result was obtained for yttrium ion implantation into alumina

[en] Thermally Stimulated Luminescence (TL) and Optically Stimulated Luminescence (OSL) properties of quartz and α-Al₂O₃ have been investigated. Anneling-induced OSL and TL sensitivity changes in quartz has been investigated by experiments and modelling. This study does not support a pre-dose effect to account for the observed annealing-induced sensitivity change. The experimental data indicates a more simple mechanism that involves alteration of the concentration of the defect centers. Results from modelling of removal or creation of defect centers comparing well with experimentally obtained data. Thermal quenching of luminescence for the main emission center, the F-center, in α-Al₂O₃:C has been investigated by analysing TL curves obtained at different heating rates. The thermal quenching dependence of luminescence is found to follow the classical Mott-Seitz expression. Basic investigations of OSL properties of αAl₂O₃:C, including: the thermal depth of the OSL traps, the temperature dependence of OSL, and the OSL stimulation spectra. Simultaneous measurements of TL and thermally stimulated conductivity (TSC) are presented for γ-irradiated αAl₂O₃:C. Activation energy analysis of the data reveals a superposition of several first-order TL and TSC peaks caused by release of charge carriers from a distribution of trapping states. Furthermore a description of an experimental method developed to determine the sign of the thermally released charge carriers has been presented. (au)

[en] Experiments were conducted to determine the loss of TL information when α-Al₂O₃:C, previously exposed to ionising radiation, is subsequently exposed to visible light. It has been shown that fluorescent as well as incandescent light induces fading in α-Al₂O₃:C. The loss of TL signal following 10 min of exposure to 300-450 1x of fluorescent and incandescent light was found to be 83% and 33% respectively. Using yellow light reduces this figure to 16%. However, for long exposure time up to three hours, 95% of the TL signal fades irrespective of the type of light sources used. The high sensitivity of α-Al₂O₃:C with its relatively lower effective atomic number, makes it an excellent candidate for applications such as personnel and especially environmental dosimetry. However, in both of these applications great care should be used to eliminate any possible exposure of this material to light. (author)

[en] Study on temperature dependence of internal resistance, R_IN, of solid electrolytic cell - air, PZ/ZrO₂+10%Y₂O₃/Pt, air - after different hold time in neutron flux is carried out. The cell internal resistance was measured within the range of 950-1300 K in isothermal mode through automated bridge of the R-5058 alternative current with operating. The cell was irradiated in the F-1 reactor central channel up to thermal neutron fluence of F₁=5.91x10¹⁷ m^-2 and F₂=1.8x10¹⁸ m^-2. It is shown that after three-hour irradiation (F₁) the systematic deviation of the δ measured values is observed at T≥1000 K, whereas after nine-hour irradiation (F₂) this effect is noted at much more lower temperature. The experimental value scattering relative to calculational one does not exceed 2%. It is found that radiation effect did not cause systematic decrease in electromotive force of the cell. This indicated the possibility for practical application of such cells under conditions discussed herein

[en] The Oarai Branch of Institute for Materials Research of Tohoku University is the facility open for university researchers whose major concern is radiation effects on materials and fuels. To satisfy a variety of demands from the researchers, we are carrying out the irradiation in the JMTR, under the following guidelines, with close cooperation with concerned JAERI laboratories. 1. Prompt response to need of the researches. 2. Minimizing radiation hazards to the researchers. 3. Irradiation under well-controlled conditions. 4. Real time measurements of radiation effect in the reactor. The current major research topics in the university groups can be categorized into following four. 1. Establishing the neutron correlation with well-defined irradiation conditions. 2. Developments of highly irradiation resistant materials. (Developing evaluation techniques using miniature specimens.) 3. Study of dynamic radiation effects. 4. Study of materials containing actinide elements. In this paper, we will describe the general status of our activities in the reactor irradiation and the post irradiation experiments, briefly. The major part will be devoted to our efforts on the in-situ experiments in the JMTR. (author)

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No abstract available

[en] In 1997 fiscal year, elucidation of plantation mechanism on cubic (3C-SiC) epitaxial film prepared by low pressure CVD method before last fiscal year at atomic level, and evaluation on Schottky junction formed onto the epitaxial film were conducted. On conducting control technology, an evaluation on ion implantation and post annealing effect under high temperature less than 800degC from both sides of structural and electrical properties was conducted. And, an observation of microprobe induced charge distribution for an object of Si On Insulator (SOI) with high radiation resistance on micro feature evaluation for element structure of heat and radiation resistant semiconductor was also conducted. (G.K.)

[en] The temperature dependence of photoinduced change of magnetic permeability (PICMP) in monocrystals Y₃Fe₅O₁₂:Si is studied. The studied temperature range is 77-300 K. The experimental results demonstrate noticeable changes in photomagnetic properties of mono- and polycrystals, as well as monocrystals grown by different, frequently rather insignificantly methods. It is assumed that these differences are related to the inhomogeneous distribution of an alloying impurity over the crystal volume, as well as the presence of uncontrolled additions and oxygen vacancies in it. The maximum temperature, when PICMP was observed, is 265 K

[en] Diffusion during He⁺, Ne⁺, and Xe⁺ irradiations of trace amounts of Au in melt-spun amorphous Pd/sub 78/Cu₆Si/sub 16/ has been experimentally investigated. Diffusion constants were measured by following the changes in ion-implanted Au profiles with Rutherford-backscattering spectrometry. Heat treatments and simultaneous irradiations were performed as a function of temperature (533--588 K), ion flux, and ion mass. Total integrated fluences being very small, ion-beam-mixing effects are negligible. More than an order of magnitude enhancement in the diffusion was observed because of irradiations. This enhancement saturates at higher fluxes, the level being independent of ion mass, i.e., independent of collision-cascade parameters. Except at higher temperatures, where the enhancement decreases, the temperature dependence of the diffusion-saturation level is similar to that of the diffusion without irradiation. The data suggest that vacancylike defects play a significant role in the diffusion