THE PHASE-DIAGRAM OF THE NEW SUPERCONDUCTOR SR2CUO2(CO3)(1-X)(BO3)(X)

A phase diagram for the boron-doped new superconductor Sr2CuO2(CO3)(1- x)(BO3)(x) has been systematically investigated The parent compound Sr 2CuO2(CO3) is an antiferromagnetic (AF) insulator with a Neel temperat ure of T-N similar to 285 K. T-N of Sr2CuO2(CO3)(1-x)(BO3)(x) changes drastically with increasing boron content x. In the lightly doped AF s tate (0 less than or equal to x less than or equal to 0.04), the stron g superexchange interaction within the CuO2-layers still yields a long -range AF ordering. The superconductivity is confined to the narrow co mpositional range 0.04 less than or equal to x less than or equal to 0 .15 and its highest T-c is 32 K at x = 0.15.