(BI,M)SR2(R,CE)NCU2OY (M=CU, CD, R=ND, GD, N=1, 2, AND 3) - A FAMILY OF SUPERCONDUCTORS THAT EXHIBIT SUPERCONDUCTIVITY AT T(C)SIMILAR-OR-EQUAL-TO-20-K FOR N=3 WITH DOUBLE FLUORITE BLOCKS AND MONOLAYER (BI,M)O SHEETS

We report the discovery of a family of Bi-based superconductors, (Bi,M )Sr2(R,Ce)nCu2Oy (n = 1,2,3), one member of which (n = 3) exhibits bul k superconductivity at T(c) = 20 K. The crystal structures of these ma terials are similar to those of (Tl, Cu)Sr2(R, Ce)nCu2Oy, but the Tl-b ased 1:2:3:2 phase (n = 3) shows semiconductive behavior. These compou nds contain Cu perovskitelike units and zero, one, and two fluorite un its, respectively. They are sandwiched between monolayer Bi-O sheets, but while the Cu perovskitelike units are separated by bilayer Bi-O sh eets in Bi2Sr2CanCun+1Oy (n = 0, 1, and 2), it is found that supercond ucting transition temperatures decrease sharply when the spacing betwe en CuO2 planes increases. It provides evidence of the effect of the co upling between successive Cu perovskite units and of the stacking patt ern of adjacent Cu sheets on the superconductivity.