SUPERCONDUCTIVITY IN LA-DOPED BI-2201

La3+ substitution into the Bi 2201 structure, of the ''ideal'' composition Bi2Sr2CuOdelta, has been investigated by means of an extensive phase diagram study into the solid solution formation al 885-degrees-C in air. Single phase solid solutions may be represented by the formula Bi2+xSr2-x-yLayCuOdelta, where y has a maximum value of 0.6, With increasing La content, the crystal symmetry changes from orthorhombic to tetragonal and the incommensurate supercell becomes less pronounced, as indicated by a decrease in intensity of the supercell X-ray powder reflections. Superconducting T(conset) values vary systematically with cation contents x, y and oxygen content delta; a maximum T(c) of 36.5 K is observed for composition x= -0.05, y=0.4.