Title :
Potential of polycrystalline YBCO layers for applications
Author :
Hein, M. ; Hill, F. ; Muller, G. ; Piel, H. ; Schneider, H.P. ; Strupp, M.
Author_Institution :
Bergischen, Univ. Wuppertal, Germany
fDate :
3/1/1993 12:00:00 AM
Abstract :
The granular properties of polycrystalline YBCO layers are characterized by their surface impedance, Z/sub s/, measured as a function of temperature, frequency and magnetic field. A model for Z/sub s/, based on grain-boundaries acting as resistively and inductively shunted Josephson junctions, is used for a conclusive analysis of the field sensitivity of Z/sub s/ and of the frequency dependence of the surface resistance. It is shown that reducing the granular character of polycrystalline samples leads to a lower absolute level and to a stronger frequency dependence of R/sub s/. As a result, the frequency-dependent improvement r=R/sub s/(Cu)/R/sub s/(YBCO), as well as the frequency at which r=1, can be increased.<>
Keywords :
barium compounds; electric resistance measurement; grain boundaries; grain size; high-temperature superconductors; microwave measurement; scanning electron microscope examination of materials; superconducting thin films; surface conductivity; yttrium compounds; 21.5 GHz; 77 K; SEM; YBaCuO polycrystalline layers; field sensitivity; frequency dependence; grain size; grain-boundaries; granular properties; high temperature superconductor; inductively shunted Josephson junctions; magnetic field; resistively shunted Josephson junction; surface impedance; surface resistance; temperature dependence; Frequency dependence; Frequency measurement; Impedance measurement; Josephson junctions; Magnetic field measurement; Magnetic properties; Surface impedance; Surface resistance; Temperature sensors; Yttrium barium copper oxide;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
