We present the model of superconducting ceramics using the single band
extended Hubbard Hamiltonian. We investigate the simultaneous presence of
antiferromagnetism (AF) and d-wave superconductivity (SC) in the coherent
potential (CP) approximation applied to the on-site Coulomb repulsion U. We
consider the hopping interaction, Δt, the inter-site charge-charge
interaction, V, (creating SC), and the single site Hund's type exchange
interaction, Fin, (creating AF). The influence of these interactions on
the separation of superconducting and antiferromagnetic phases near the
half-filling point is investigated. Results are compared with the experimental
data for YBaCuO and NdCeCuO compounds.Comment: 4 pages, 4 figure