摘要:

Radiation damage at high doses (approaching or exceeding one displacement per atom) has been studied widely in metals and alloys in view of its importance in fission and fusion reactor technology. Insulators have received less attention, but their use-actual or potential-in reactors and as host materials for radioactive waste has stimulated recent studies. Insulators present conceptual problems compared with metals: electronic as well as atomic processes may contribute to radiation damage and different sub-lattices may not be affected by radiation in the same way. Ionization damage (radiolysis) in NaCl at high doses and temperatures provides a model system where the production of metal and halogen-based defect clusters can be studied experimentally and theoretically in some detail. It also has direct practical relevance to the storage of high-level radioactive waste in salt repositories. Fast neutron damage to high doses will be sustained by insulators used in any future fusion reactors. Basic studies of the formation of voids and dislocation structures in AI,O, irradiated with neutrons, ions or fast electrons show how the processes depend on displacement dose and temperature.

ISSN:0033-7579    

DOI:10.1080/00337578608226004

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The ultrasonic attenuation of longitudinal acoustic waves in slightly disordered crystalline quartz has been measured over a temperature range from 1.3 to 300 K, using the pulse-echo technique. Neutron irradiation is demonstrated to increase the ultrasonic attenuation at low temperatures indicating the presence of two-level tunneling systems similar to those of glasses. Our low-temperature acoustic results agree with a frequency independence and aT3behaviour for the relaxation process predicted by the two-level tunneling TLS-model where the regime ωT1≫ 1 holds.

ISSN:0033-7579    

DOI:10.1080/00337578608226005

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Static magnetic susceptibilities have been measured on an α-quartz single crystal that had been irradiated with fast neutrons. Above 65 K, the radiation-induced paramagnetism obeys the Curie law, indicating the presence of non-interacting centres. The low-temperature measurements result in a field-dependent susceptibility comparable to the effect of the Brillouin saturation of non-interfacing centres. The average moment per centre, however, is higher than the one due to the spin only of single unpaired electrons, pointing to ferromagnetically coupled electron pairs. When the calculated susceptibility values, as obtained from the derived moments and concentrations using the Brillouin theory, are subtracted from the measured data, then the differences behave—over the whole temperature range—as the susceptibility of antiferromagnetically coupled electrons. On the same sample also, low-temperature 20.9 GHz ESR measurements have been carried out. The major resonance line is attributed to theE’ centre. The general behaviour clearly corroborates the presence of interactions; the effect does not show anisotropy.

ISSN:0033-7579    

DOI:10.1080/00337578608226006

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

High dose56Fe implantations (15–110 keV) in oxygen ion conducting solid solutions of 0.86 Zr02-0.14 YO1.5[ZY14] are used to introduce electronic conductivity. The Fe distribution in the target as a function of the various implantation parameters (dose, acceleration voltage) has been studied. Different profile shapes can be obtained. A combination of a high surface concentration and a rather flat profile in a surface layer is possible. Strong deviations from the normally expected Gaussian distribution are found after high dose implantation due to sputtering effects. However, if the sputter yield is experimentally determined, good prediction of the implanted dopant distribution is still possible. The peak concentration of high dose distributions is situated at or close to the surface. This surface peak concentration is obtained at a steady-state situation of concurrent sputtering and implantation of Fe. A maximum surface concentration with respect to Zr(Fe/Zr = 1.0) is achieved with the highest implantation energy used (110 keV) because the sputter yield is relatively low as compared with lower energies. After prolonged heat treatment in air (800°C, 24–60 hours) of the samples implanted with a high dose Fe, Fe203-rich surface layers are formed. Rutherford Backscattering Spectrometry (RBS) is used for the profile analyses in combination with Auger Electron Spectroscopy (AES).

ISSN:0033-7579    

DOI:10.1080/00337578608226007

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The dc electrical conductivity of high purity, polycrystalline alumina has been measured during exposure to 60 kV peak X-irradiation and 20 MeV proton irradiation at temperatures up to 700°C. In the absence of radiation the conductivity was found to have an activation energy of 0.30 ± 0.01 eV below ∼ 280°C and 1.41 ±0.01 eV at higher temperatures. Under irradiation the apparent activation energy was reduced to 0.06 ± 0.01 eV at low temperature and varied with the type of irradiation at higher temperature. The radiation-induced conductivity was found to follow a power law with dose rate in which the dose rate exponent, δ, varied in a complex manner with temperature. With X-irradiation δ was approximately unity at low temperatures, then fell to a minimum of 0.7 at ∼ 225°C, after which it rose to an intermediate value. Under proton irradiation the dose rate dependence was supralinear with δ = 1.25 up to a temperature of ∼ 500°C after which it fell to a minimum of 0.58 at 630°C before increasing to become supralinear again at higher temperatures. It is proposed that the supralinear behaviour during proton irradiation follows from displacement damage creating aluminium vacancy centres which behave as hole traps with an extended density of states within the band gap.

ISSN:0033-7579    

DOI:10.1080/00337578608226008

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

MgO single crystals were implanted with 40 keV H2+and 60 keV C+ions. The diffusion behavior of the implant species in the temperature range 25–500°C was studied by SIMS depth-profiling. The1H+andl2C−SIMS profiles show practically no movement of implanted species. The results suggest that both hydrogen and carbon are tightly bound in the MgO, most likely as OH−and CO32-ions.

ISSN:0033-7579    

DOI:10.1080/00337578608226009

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Simultaneous measurements of optical absorption, TL, and TSC, for two MgO samples containing 180 and 650ppm Fe, y-irradiated at 14 and 100°C, show the importance of iron in the TL and TSC processes, and indicate that the TSC peaks observed above about 90°C are due to electrons. As in earlier work the red TL emission is observed to be due to Fe2+. With increasing iron content, V-type centres associated with Fe2+play an important role.

ISSN:0033-7579    

DOI:10.1080/00337578608226010

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The dielectric properties (εand tan δ) of aluminium oxynitride (AlON), and two grades of commercial alumina (99.9% and 97.5% A1203) have been measured after neutron irradiation doses to faiences ranging from 1017to 1020n/cm2. The measurements span the frequency range 0.1 to 65 MHz and thus include the ion cyclotron resonance frequencies currently being considered for plasma heating in fusion reactors. The permittivity (Ψ) has been measure by a two fluid technique with an accuracy of better than + / - 1%. A 2% increase in permittivity has been observed after irradiation to 1019n/cm2.

ISSN:0033-7579    

DOI:10.1080/00337578608226011

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Measurements by differential thermal analysis, between room temperature and 1100°C, of the stored energy induced in MgO samples either by irradiation with 1.8 MeV electrons, or plastic deformation or thermal quenching, indicate that these treatments induce a similar type of damage. The energy released ranges between 102oand 1021eV. g−1, which points to the formation of a large number of lattice defects which are aggregated in a variety of clusters or extended defects. Optical absorption measurements of the evolution of anion and cation vacancies after X-irradiation following isochronal annealing up to 1100°C support this proposal.

ISSN:0033-7579    

DOI:10.1080/00337578608226012

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Powder mixtures are difficult to analyze since they give complex X-ray diffraction patterns where the patterns of the components are superimposed one over the other with very little indication of which diffraction lines belong to which compound.

ISSN:0033-7579    

DOI:10.1080/00337578608226013

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor