Transport mechanisms in Y1Ba2Cu3O6+ superconductors in the metallic and the semiconducting regimes

We report measurements of the electrical resistivity at high temperatures for constant oxygen content, or for fixed temperature and varying oxygen content. We show that the Y1Ba2Cu3O6+ compound changes from a metallic to a semiconducting behavior for 0.5. In the semiconducting regime, the characteristic activation energy is oxygen dependent and reaches 0.37 eV for =0.25. In the metallic regime, the conductivity is approximately linear in the oxygen content while on the semiconducting side, excess conductivity arises from thermally activated processes. © 1988 The American Physical Society.