Low temperature resistivity of Au-YBa2Cu3O7-delta sintered materials: influence of porosity and secondary phases

Author: Lambert C.   Marfaing J.   Debierre J-M.  

Publisher: Taylor & Francis Ltd

ISSN: 1362-3036

Source: Philosophical Magazine Letters, Vol.79, Iss.6, 1999-06, pp. : 369-374

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Abstract

The resistivity rho of sintered Au and YBa2Cu3O7-delta(Au and YBCO) mixed powders is measured at T = 60K, as a function of the gold volume fraction phi . The samples retain zero resistivity up to phi = phi c = 0.62. In the range phi [phi c, 1], the curve rho (phi) is bell-shaped, with a maximum at phi 0.75. Scanning electron microscopy observations suggest that the increase of resistivity can be attributed both to porosity and to secondary phases inducing contact resistances between YBCO and Au grains. A random conductor network model is used to test the relative influence of both parameters. The numerical data show that porosity alone cannot account for the resistivity maximum. Conversely, a peak is indeed observed in the simulations when a substantial interface resistivity is imposed.