Abstract
Filamentary superconductivity have been observed below T c of 14 K for sintered-polycrystalline (Pb 0.5 Cu 0.5 ) 2 (Ba 0.5 Sr 0.5 ) 2 YCu 2 O 8 samples. Low electrical resistivity shows that this semiconducting sample is near the boundary of metal-insulator transition. The observed filamentary superconductivity indicates that the oxygen concentration of the sample (Pb 0.5 Cu 0.5 ) 2 (Ba 0.5 Sr 0.5 ) 2 YCu 2 O 8-δ is inhomogeneous. The oxygen off-stoichiometric parameter 6 plays the role of controlling the variation of free charge carriers in this electronically inhomogeneous sample where part of the sample is across the transition boundary and thus becomes superconducting. © 1996 THE PHYSICAL SOCIETY OF THE REPUBLIC OF CHINA.