Interpretation of the temperature dependence of conductivity in superconducting oxides

The diverse variations of the conductivities vs. temperature observed in oxide superconductors can be interpreted with a model based on microcanonical ensembles of a semiconductor and a semimetal originally derived for organic radical cation salts. The equation for the model transverses, through the variations of the Fermi and gap energies and a scattering factor, the range from a semiconductor to a semimetal and defines quantitatively the boundary between the two corresponding to the optimum superconducting state. Therein it describes quantitatively the roles of composition and pressure in determining the onset of the superconducting state. An examination of the published resistivity curves vs. temperature for La/sub 2-x/A/sub x/CuO/sub 4-δ/ and YBa/sub 2/Cu/sub 3/O/sub 6.5+δ/ yield information consistent with the model and relevant to the defects and range of homogeneity needed for phase diagrams