SYNTHESIS AND SUPERCONDUCTIVITY OF (HG0.7BI0.3)SR-2(CA1-XLAX)CU2O6+DELTA SYSTEM

The problems of making phase-pure (Hg0.7Bi0.3)Sr-2(Ca1-xLax)Cu2O6+delt a system for 1.0 greater than or equal to 2x greater than or equal to 0.0 are discussed in detail. This system with the tetragonal HgBa2CaCu 2O6-type (1212) structure was found only for x=0.25, 0.5 and 0.75. The a and c lattice parameters increase with the increasing La concentrat ion due to the decreasing in oxidation state of Cu and the replacement of smaller Ca+2 ions (1.12 Angstrom) by larger La3+ ions (1.16 Angstr om). The transition temperature T-c decreases as the La substitution p arameter x increase. We observed the maximal T-c at x=0.25 with 87 K a nd 72 K for x=0.5.