Iv. Roshchin et al., REENTRANT CRITICAL-CURRENT BEHAVIOR AS A COMMON FEATURE OF SINGLE GRAIN-BOUNDARY JOSEPHSON-JUNCTIONS IN BICRYSTALS OF COPPERLESS OXIDE SUPERCONDUCTORS, IEEE transactions on applied superconductivity, 5(2), 1995, pp. 1328-1330
Critical current and electrical transport properties of single grain b
oundaries in bulk bicrystals of the copperless oxide superconductors B
aPb1-xBixO3 and Ba1-xKxBiO3 were measured in order to investigate quas
iparticle tunneling and Josephson properties of these materials, which
hold promise for the creation of low temperature microwave electronic
s and cryogenic particle detectors, An unusual and remarkable feature
of the temperature dependencies of critical current is the non-monoton
ous behavior with sharp maximum at temperatures well below the critica
l temperature, This anomalous low temperature re-entrant behavior appe
ars to be a new universal feature of single grain boundaries in copper
less oxide superconductors. Our studies of grain boundary transport pr
operties in BaPb1-xBixO3 and Ba1-xKxBiO3 bicrystals lead us to the con
clusion that re-entrant behavior of critical current originates from c
hanges in oxygen electronic states due to heterovalent substitution in
copperless materials.