ISSN:
1572-9605
Keywords:
(Bi, Cu)-1212 phase superconductor
;
excess oxygen
;
occupancy at O(5) site
;
(Bi, Cu)-O monolayer
;
apical Cu(2)-O(2) bond
Source:
Springer Online Journal Archives 1860-2000
Topics:
Electrical Engineering, Measurement and Control Technology
,
Physics
Notes:
Abstract Comparative neutron structural investigations are made on nonsuperconducting (slow-cooled) and superconducting (liquid-nitrogen quenched;T c onset=70 K andR=0 at 20 K) samples of (Bi0.5Cu0.5)Sr2(Y0.8Cu0.2)Cu2O7 + δ in order to examine the role of excess oxygen on the superconducting behavior of this “1212”-phase compound. Analysis of refined structural parameters shows that the two main factors which influence the superconductivity in (Bi, Cu)-1212 are: (i) the extent of occupancy of excess oxygen at O(5), the 2(e) site located in between the two CuO2 pyramidal layers, and (ii) the length of the apical Cu(2)-O(2) bond. The (Bi, Cu)-O monolayer plays the role of the “charge reservoir” quite effectively as reflected by the substantial increase in the length of the apical (bridging) Cu(2)-O(2) bond due to depletion of excess oxygen in this layer. Surprisingly, vacancies at as many as 10% of the O(1) site belonging to the CuO2 planes do not appear to disrupt the flow of current in the Cu(3d)-O(2p) planar network in the superconducting state. Relevant features of the structure of the (Bi, Cu)-1212 phase, in particular the role of excess oxygen and its occupancy at different sites, are discussed in the light of the available data on the isostructural (Pb, Cu)-1212 phase and the (La, Sr, Ca)3-Cu2O6 + δ phase superconductors.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01320883
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