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  • 1
    Electronic Resource
    Electronic Resource
    Effects of thermal annealing on the magnetization dynamics of vitrovac amorphous ribbons (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1486-1489 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of thermal annealing on the frequency behavior of the initial permeability, μ0, of Vitrovac(r) 6025 amorphous ribbons have been investigated. For annealing temperatures above the Curie point, Tc, μ0 shows a significant increase (from 13 760 to 39 600) as compared with the as-quenched sample; for annealing temperatures below Tc ("aging''), μ0 decreases (from 13 760 to 7700). The domain wall relaxation frequency exhibited the opposite behavior: a decrease with annealing at T(approximately-greater-than)Tc (from 69 to 18 kHz) and an increase with aging (from 69 to 127 kHz). The frequency behavior can be modeled by means of a simple, parallel RL circuit, where the inductance value is proportional to the initial permeability, and the equivalent resistance value, which is inversely related to the damping parameter, is the same for all the samples. These results can be interpreted on the basis of a variation of the extent of domain wall pinning, as manifested in changes in the spring constant α, decreasing with annealing and increasing with aging. The relaxation frequency is proportional to the extent of pinning, and initial permeability depends on the inverse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351713
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  • 2
    Electronic Resource
    Electronic Resource
    Equation of motion of domain walls and equivalent circuits in soft ferromagnetic materials : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7000-7002 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The equation of motion for ferromagnetic domain walls is compared with initial permeability measurements of Co-based soft ferromagnetic amorphous ribbons at frequencies in the range 100 Hz–13 MHz. The analysis of these results by complex permeability methods leads to an equivalent circuit formed by a parallel RL arrangement in series with a small resistance RW due to resistance of the measurement coil. This equivalent circuit, however, cannot model the irreversible magnetization behavior for fields higher than the pinning (or propagation) field. It is shown that the equation of motion is also consistent only with the reversible magnetization mechanism, if the displacement term, x, represents instead the bulging of the pinned wall. The correlations between the terms in the equation of motion and the elements of the equivalent circuit are established.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356756
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of nanocrystallization upon the soft magnetic properties of Co-based amorphous alloys : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6940-6942 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphous samples of Vitrovac(R) 6025 metallic alloys were nanocrystallized by thermal annealing at temperatures in the range 576–716 K, well below the crystallization temperature (831 K, as obtained by differential scanning calorimetry at 20 K/min) and times in the range 10–90 min. Initial magnetic permeability exhibited a maximum of ∼109 000 (from ∼20 000 for the as-quenched state) for annealing times of ∼15 min, and then a decrease toward a plateau value (30 000–40 000) for longer times. Domain wall relaxation frequency showed the opposite behavior, a minimum of ∼9 kHz (from 40 kHz for the as-quenched value) for the permeability maximum, and then a stabilization at ∼15 kHz. Transmission electron microscopy observations confirmed that for annealing times up to 60 min., crystallite size is smaller than 30 nm. Permeability and relaxation frequency results are interpreted in terms of the dependence of wall bulging on anisotropy and free-wall surface area between pinning sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356788
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  • 4
    Electronic Resource
    Electronic Resource
    Domain wall relaxation in amorphous ribbons (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5589-5591 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Monodomain, polycrystalline hexagonal ferrites (BaFe12O19) and amorphous ribbons (Vitrovac 6025) were measured as a function of frequency with rf magnetic fields from 5 Hz to 13 MHz of various amplitudes. Monodomain ferrites showed the features of the spin rotation magnetization mechanism, while amorphous ribbons showed the low-frequency dispersion generally attributed to domain wall relaxation. However, at relatively high applied fields, a third dispersion is resolved at lower frequencies from domain wall relaxation, which can be attributed to magnetic hysteresis. By using some of the complex impedance formalisms, the relaxation character of domain wall bulging is confirmed, while hysteresis dispersion exhibited a complex behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345893
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  • 5
    Electronic Resource
    Electronic Resource
    High oxide ion conductivity in Ca 12 Al 14 O 33 (1988)
    [s.l.] : Nature Publishing Group
    Nature 332 (1988), S. 525-526 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The aluminate Ca12Al14O33 is a stable ceramic material, well known from its occurrence in cement clinkers. It can be prepared by solid state reaction of CaCO3 and A12O3 mixtures in platinum crucibles at 1,200-1,350 °C for 1-2 days; its melting point is variously quoted as being in the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/332525a0
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  • 6
    Electronic Resource
    Electronic Resource
    Ca12Al14O33 — A possible high-temperature moisture sensor (1989)
    Springer
    Journal of applied electrochemistry 19 (1989), S. 410-412 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract C12Al14O33 is a high temperature oxide ion conductor whose conductivity is very sensitive to the presence of water vapour for temperatures in the range ∼ 1000 to 1200° C. The changes are reversible and the conductivity may be recovered by heating in a dry atmosphere. Applications in an amperometric device are envisaged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01015244
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  • 7
    Electronic Resource
    Electronic Resource
    Production of tartrate and glycolate from the electrochemical reduction of glyoxylate (1994)
    Springer
    Journal of applied electrochemistry 24 (1994), S. 271-273 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242896
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  • 8
    Electronic Resource
    Electronic Resource
    Optimization of superconducting critical temperatures by control of cation and anion stoichiometry in Bi2Sr2CaCu2Oδ-based solid solutions (1995)
    Springer
    Journal of materials science 30 (1995), S. 2743-2746 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract T c data are reported for powders of cation-stoichiometric Bi2Sr2CaCu2Oδ and for nonstoichiometric samples based on the three mechanisms Bi⇄Sr, Sr⇄Ca and Sr vacancy. For each, the T c values depend critically on the final oxygen contents, which were varied by heating samples in either O2 or N2 at different temperatures. Stoichiometric Bi2Sr2CaCu2Oδ has the highest T c, 92 K, obtained after heating in O2 at ∼ 820 °C. Heating in O2 at lower temperatures gives rise to overdoping and T c decreases to 60 K. The other cation compositions show a smaller maximum T c but also less reduction in T c on overdoping. Under-doped samples, with reduced T c values were obtained on heating in N2. These data, together with selected literature results, lead to a unified picture of the variation of T c with cation composition and oxygen content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349639
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  • 9
    Electronic Resource
    Electronic Resource
    Sinterability of commercial 8 mol% yttria-stabilized zirconia powders and the effect of sintered density on the ionic conductivity (1998)
    Springer
    Journal of materials science 33 (1998), S. 4297-4305 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The sintering behaviour of a number of commercially produced 8 mol% yttria-stabilized zirconia powders has been studied. The effect of different sintering regimes on the density and microstructure of the sintered ceramic was determined using density measurements, scanning electron microscopy (SEM) and dilatometry. The chemical homogeneity, particle size and the morphology of the as-received powder were related to the sintering behaviour of the different commercial powders. Powders prepared via a route which involved a spray-drying step sintered more readily than those prepared without a spray-drying step. Plasma-derived powders did not sinter to as high an apparent density as co-precipitated powders. The effect of sample density on the ionic conductivity of sintered YSZ ceramics was studied using a.c. impedance spectroscopy. This technique allowed separation of the bulk and grain-boundary components, enabling clear intepretation of the effects of sample porosity of the conduction pathways. Ceramics prepared from the three different powders achieved a bulk ionic conductivity of ∼16 S cm-1 at 1000 °C for sintered densities of 95% or greater. The results obtained are compared to values reported for a variety of other commercial powders. © 1998 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004435504482
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  • 10
    Electronic Resource
    Electronic Resource
    Oxide ion transport in highly defective cubic stabilized zirconias (1995)
    Springer
    Ionics 1 (1995), S. 279-285 
    Details
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ac impedance spectroscopy and neutron powder diffraction have been used to study the high temperature behaviour of defective fluorite solid electrolytes. In yttria-stabilised zirconia with an yttrium content of 15 mol% YO1.5 there is a marked change in conductivity behaviour at around 650 °C, with a decrease in activation energy of 0.15 eV. Structural studies confirm that this is due to a change in the bulk of the sample with the disappearance of diffuse scattering peaks and marked changes in the behaviour of the isotropic temperature factors at the same temperature. These results indicate that the change in activation energy of yttria-stabilised zirconia at 650 °C is due to an order-disorder transition involving local defect clusters. In studies of zirconia co-doped with yttrium and niobium, activation energy for conduction is found to rapidly increase with the concentration of the trivalent yttrium Saturation doping is reached at about 20–30 % of yttrium and activation energy only increases slightly with doping. Introduction of pentavalent niobium at this level of doping serves to decrease activation energy, although it also decreases conductivity slightly. The low and high temperature activation energies converge as the saturation regime is approached. These observations seem to suggest that ordering of defect clusters into microdomains increases activation energy for ionic motion. At low defect concentrations and high temperatures, this local ordering breaks down and the activation energy for conduction decreases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02390208
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