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  • 1
    Electronic Resource
    Electronic Resource
    Positron Annihilation Lifetime Spectroscopy of Air-Fired Ca(1−x)(La)xTiO3 Perovskites (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In polycrystalline air-fired perovskites of Ca(1−x)(La)xTiO3 stoichiometry (x=0.00–0.15), the positron annihilation lifetime increased monotonically with x, and showed an ∼40% increase of the lifetime at x∼0.1, at which value the lifetime increase saturated. These data, together with measured perovskite stoichiometry, indicate that equal numbers of Ca and Ti vacancies were the prime charge compensators. Thermal gravimetric data are consistent with charge compensation occurring via the cation vacancies in the air-fired samples and Ti3+ in equivalent samples prepared under reducing conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.00045.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effect ofV K centers on positron annihilation in KCl and Ag-doped KCl (1974)
    Springer
    Applied physics 4 (1974), S. 83-86 
    Details
    ISSN: 1432-0630
    Keywords: Positron annihilation ; Color centers ; Radiation damage in ionic solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Positron lifetime spectra have been measured at 77 K for KCl and Ag-doped KCl before and after x-irradiation at 77 K and after annealing at room temperature. Radiation at 77 K reduces the intensity of the intermediate lifetime (τ2) component. Radiation-induced defects were monitored optically and by ESR. The experiment shows that the changes observed in the positron decay are associated with the presence ofV K centers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00884158
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Positron annihilation in γ-irradiated pure and Mg-doped LiF (1974)
    Springer
    Applied physics 4 (1974), S. 75-78 
    Details
    ISSN: 1432-0630
    Keywords: Positron annihilation ; Color centers ; Radiation damage in ionic solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Positron annihilation lifetime spectra in unirradiated and γ-irradiated pure LiF and heavily doped LiF∶Mg have been resolved into three components. The intensity of the intermediate lifetime component increases in proportion to theF-center concentration for both materials until saturation occurs (≈1.4×1017 cm−3 in LiF and ≈5.7×10−17 cm−3 in LiF∶Mg). The presence of a large positive ion vacancy concentration appears to have a much smaller effect than has been observed in KCl∶Ca.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00884156
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  • 4
    Electronic Resource
    Electronic Resource
    Positron annihilation in alpha- and beta-cyclodextrin (1978)
    Springer
    Applied physics 15 (1978), S. 85-87 
    Details
    ISSN: 1432-0630
    Keywords: 78.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We have measured positron annihilation lifetimes in α- and β-cyclodextrin samples both in air and in vacuum. The existence of different hollow spaces in these clathrates offers a good test of the “free volume” model of positronium decay in molecular solids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00896895
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  • 5
    Electronic Resource
    Electronic Resource
    Positron annihilation lifetime spectral changes on dehydration of natural beryls and cordierites (1980)
    Springer
    Physics and chemistry of minerals 6 (1980), S. 47-53 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The effect on positron annihilation lifetime spectra, measured at room temperature, of the dehydration of single crystals of beryl and cordierite was studied. In each case, the spectra were satisfactorily fitted to three lifetime components. For the beryls, the dehydration considerably enhanced the intensity of the intermediate-lifetime component (I 2) and reduced the intensity of the longest-lived component (I 3). I 2 is attributed to positron annihilation in the empty cages in the channels of the beryl structure and I 3 to annihilation by a pick-off process via unknown foreign molecules. However, for the cordierites, the main effect of the dehydration was a slight (∼10%) increase in the lifetime of the intermediate component, τ2. Here I 2 was relatively high both before and after dehydration and the increase in τ2 is attributed to Si-Al ordering. No changes in the lifetime spectra were produced by γ irradiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308393
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    Paper (German National Licenses)
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