Bose-Einstein Condensation Picture of Superconductivity in YBa2 Cu3 O7 (91 K) and YBa2 Cu3Se7 (371 K). (Dilute metals)
A metal dilution degree in the compounds YBa2 Cu3 O7 and YBa2 Cu3Se7 is defined as z=(rMe/rO2-;Se2-)3. A substitution of oxygen by selenium changes z by 8 times and the Bose-Einstein condensation temperature equals TcSe = TcO*8 2/3 = 364 K. The "active" electron pairs density in YBa2 Cu3 O7 is about 1.7 1020 cm-3. The electron effective mass is about 5me and is proportional to the dielectric constant.