  We report the observation of cluster (local) superconductivity in the
magnetoelectric Pb(Fe1/2Sb1/2)O3 ceramics prepared at a hydrostatic pressure of
6 GPa and temperatures 1200-1800 K to stabilize the perovskite phase. The
superconductivity is manifested by an abrupt drop of the magnetic
susceptibility at the critical temperature TC 7 K. Both the magnitude of this
drop and TC decrease with magnetic field increase. Similarly, the low-field
paramagnetic absorption measured by EPR spectrometer drops significantly below
TC as well. The observed effects and their critical magnetic field dependence
are interpreted as manifestation of the superconductivity and Meissner effect
in metallic Pb nanoclusters existing in the ceramics. Their volume fraction and
average size were estimated as 0.1-0.2% and 140-150 nm, respectively. The
superconductivity related effects disappear after oxidizing annealing of the
ceramics.
