Vanishing of superconductivity at a transition from itinerant-electron to small-polaron conduction in nominal Bi4-xPbx(Sr3Ca)Ca2-xYxCu4O16
Abstract
Lead was found to substitute for bismuth on cosubstitution of yttrium for calcium in nominal Bi4(Sr3Ca)Ca2Cu4O16. Variations with x in the lattice parameters, the oxidation parameter determined by iodometric titration, and the temperature dependence of resistance have revealed a correlation of the variation of Tc and c parameter versus x with a metal-to-semiconductor transition. It is argued that this correlation manifests a transition from itinerant-electron to small-polaron conduction. This conclusion is related to the observed shifts in c-axis oxygen that appear to be associated with a transition from antiferromagnetic semiconductor to a superconductor in other copper-oxide systems.
- Publication:
-
Applied Physics Letters
- Pub Date:
- December 1988
- DOI:
- 10.1063/1.100548
- Bibcode:
- 1988ApPhL..53.2695M
- Keywords:
-
- Bismuth Compounds;
- Electron Transitions;
- Polarons;
- Superconductivity;
- Copper Oxides;
- Crystal Lattices;
- Electrical Resistivity;
- Oxidation;
- Perovskites;
- Temperature Dependence;
- X Ray Diffraction;
- Solid-State Physics