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  • 1
    Electronic Resource
    Electronic Resource
    Mixed Electronic-Ionic Conductivity of Cobalt Doped Cerium Gadolinium Oxide (2000)
    Springer
    Journal of electroceramics 5 (2000), S. 231-243 
    Details
    ISSN: 1573-8663
    Keywords: ceria solid solutions ; mixed ionic electronic conductivity ; nanosized ceramic ; transition metal oxides ; cobalt oxide ; brick layer model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effect of small amounts (〈5 mol %) of cobalt oxide on the electrical properties of cerium oxide solid solutions has been evaluated. Ce0.8Gd0.2O2-x (CGO) powder with an average crystallite size of 20 nm served as a model substance for the electrolyte material with a high oxygen ion conductivity and low electronic conductivity in its densified state. Doping the CGO powder by transition metal oxides (MeO) with concentrations below 2 mol % did not change the ionic conductivity nor the electrolytic domain boundary. After long sintering times (2 h) at temperatures above 900°C, MeO and CeO2 form solid solutions. However, short sintering times or high dopant concentrations lead to an electronic conducting grain boundary phase short circuiting the ionic conductivity of the CGO grains. Choosing proper doping levels, sintering time and temperature allows one to tailor mixed conducting oxides based on CGO. These materials have potential use as electrolytes and/or anodes in solid oxide fuel cells and ion separation membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026583629995
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  • 2
    Electronic Resource
    Electronic Resource
    Spatial and force resolution of magnetic force microscopy in current imaging (1999)
    Springer
    Czechoslovak journal of physics 49 (1999), S. 1567-1574 
    Details
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Magnetic force microscopy (MFM) can be used to image current distributions in current leads of sub-micron dimensions. Here we present a systematic study about the spatial and force resolution of such currents. In the case of force resolution, we studied the least measurable magnetic force of MFM for different sample currents. The analysis of images from parallel Al conducting plates are combined with those from force-distance curves and finite element calculations. Several interacting regimes between the magnetic tip and the currents are found and interpreted. It is shown that model calculations are necessary even for qualitative image interpretation. Then spatial resolution in the range of 100 nm can well be obtained and quantitative studies of current distributions on widths of 10 nm resolution are possible in special cases. The approach is demonstrated in imaging the current distribution in superconducting Bi2Sr2CaCu2O x single crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022867731052
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  • 3
    Electronic Resource
    Electronic Resource
    Texture in Melt-Processed Bi-2212 (1997)
    Springer
    Journal of electroceramics 1 (1997), S. 133-144 
    Details
    ISSN: 1573-8663
    Keywords: Bi2.2Sr2.055Ca0.95Cu2Ox ; high temperature superconductor ; partial melt processing ; thick films ; texture ; grain alignment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The high temperature superconducting phaseBi2.2Sr2.055Ca0.95Cu2Ox (Bi-2212) decomposes peritectically when heated above itssolidus temperature and reforms during slow cooling from the partiallymolten state. In thick films of 60 µm the Bi-2212 grains grow directlyfrom the melt when cooled at a rate of 5 K/h in oxygen atmosphere. Theorientation of the nuclei in the melt is random. After nucleation the grainsgrow anisotropically, leading to a mica- or platelet-like morphology. Upongrowth the Bi-2212 platelets encounter several obstacles, i.e. the sampleboundaries, second phase grains and other platelets. Various reactions occurwhen their growth is hindered. They stop growing, change the direction ofgrowth or even grow through the obstacle. A mechanism is proposed whichallows small grains to turn themselves into a favorable orientation at theirinitial stage of growth. At the end of the partial melting process, thesemechanisms lead to a textured microstructure in thick films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009972632563
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