THE CORRELATION BETWEEN SUPERCONDUCTIVITY AND CU-O BOND LENGTH FOR THE SINGLE CU-O LAYER COMPOUNDS WITH THE BI2SR2CUO6+DELTA-TYPE (2021) STRUCTURE

Abstract

The structure and superconductivity in the single Cu-O layer bismuth (2021) system can be stabilized also by the doping of Na1+ ions. Contrary to the La-doped Bi2(Sr,La)2CuO6+delta system with T(c) enhancement up to 35 K. T(c) remains around 10 K for the Na-doped Bi2(Sr2-xNax)CuO6+delta system (0.0 less-than-or-equal-to x less-than-or-equal-to 0.4). The variation of T(c) with the Cu-O bond length r(Cu-0) in the Cu-O layer for the Bi family which consists of the systems (Bi,Pb)2Sr2CuO6+delta, Bi2(Sr,Na)2CuO6+delta, Bi2(Sr,La)2CuO6+delta and (Bi,Pb)2(Sr,La)2CuO6+delta indicates an optimum r(Cu-0) value of 1.906-1.913 angstrom with maximum T(c) of 35 K for these Bi(2021) compounds.