INFLUENCE OF BA CONTENT AND CE DOPING ON THE STRUCTURAL FEATURES OF YBA2CU4O8 SUPERCONDUCTOR - A NEUTRON STUDY

The structures of A: YBa2Cu4O8 (T(c) = 80 K), B: Y0.9Ce0.1Ba2Cu4O8 (T( c) = 55 K), and C: YBa2.2Cu4O8 (T(c) = 80 K) have been investigated us ing the powder neutron technique with a view to assessing the influenc e of the bridging Cu(2)-O(4) and Cu(1)-O(4) bonds on the superconducti ng transition temperature. The Cu(2)-O(4) bond for samples A and C (wi th T(c) = 80 K) appears to be compressed as compared to the reported d ata. On the other hand, the substitution of Ce at 10% Y sites elongate s the Cu(2)-O(4) bond substantially and also brings the T(c) down to 5 5 K. The role of Cu(2)-O(4) bond length as well as other parameters ex pected to influence the T(c) behavior of Y-124 samples are discussed i n the light of the present data. The study also shows that the ambient oxygen pressure route, if tried with the starting composition YBa2.2C u4Oy, leads to a quite homogeneous 124-phase.