Bulk 2ax2bxc Superstructure in TCNQ-treated (Bi, Pb)-2223 Cuprates

[[abstract]]By reaching (Bi, Pb)-2223 cuprate superconductors with TCNQ (7,7,8,8-tetracyanoquinodimethane) in a sealed and evacuated pyrex ampoule at 300°C for 14 days, we have observed a superstructure of 2a×2b×c in a bulk form according to X-ray diffraction and transmission electron microscope analyses. The origin of the 2a×2b×c superstructure could be attributed to an ordering of oxygen vacancies in the CuO2 layers and also likely in the SrO layers. Electrical conductivity of this TCNQ treated (Bi, Pb)-2223 cuprate shows a metal-like temperature dependence with high resistivity (102 ∼ 103 Ω cm), and a relatively rapid resistivity drop at ca. 11.7 K