Properties of high T(c) superconducting oxides

The dependence of the normal and superconducting properties of (La/1-x/M/x/)2CuO/4-delta/ (M = Ba, Sr, and Ca) and Ba2YCu3O(7-delta) on composition and oxygen deficiency is systematically investigated. A two-dimensional conduction path is suggested from the relationship between the change in the lattice parameter with x and with the variation of M elements and the change in the superconducting properties of the K2NiF4-type superconductors. Specific heat measurements on (La/1-x/M/x/)2CuO/4-delta/ for M = Ca and Sr and on Ba2YCu3O7 reveal that the density of states at the Fermi level was even smaller as T(c) increases in this series. The amount of oxygen deficiency is large in K2NiF4 oxide, and is exceptionally large in Ba2YCu3O7 as an oxide. This deficiency is responsible for a variety of features which characterize the normal and superconducting properties of the oxide superconductors. 37 references