Superconductivity in ba₃la₂lucu₆o_y

Single-phase Ba₃La₂LuCu₆O_y(y͂14) is synthesized. Superconductivity is observed after annealing in oxygen at high pressure; it is a semiconductor without annealing. Power X-ray diffraction shows that annealing changes the crystal structure of Ba₃La₂LuCu₆O_yfrom tetragonal into orthorhombic. Magnetic susceptibility measurements show that T_conset of the annealed sample is around 50 K and about 1% of the volume is superconductive. The analysis shows that the average Cu valence dependence on T_cof Ba₃La₂LuCu₆O_yand Ba₂YCu₃O_7-ydiffers.