Occurrence of Superconductivity in La2-xbaxcuo4 (0-less-than-or-equal-to-x-less-than-or-equal-to-0.04) and La2-xndxcuo4(0-less-than-or-equal-to-x-less-than-or-equal-to-0.3) Systems After Fluorination

The influence of a low temperature fluorine gas treatment on structural, superconducting and transport properties of oxides with the K2NiF4 structure has been studied. When materials with the composition La2-xBaxCuO4 where 0 less-than-or-equal-to x less-than-or-equal-to 0.04 are treated under 1 bar of F2 gas at 200-degrees-C, an increase in the orthorhombic distortion (b - a) is observed and the materials become superconductors. The insertion of anionic species in the lattice is confirmed by the observation of an increase in weight and in the c-parameter and by the elemental analysis. After annealing at 200-250-degrees-C under vacuum or argon atmosphere, La2-xBaxCu(O,F)4+delta oxyfluorides lose their superconducting properties. This change is accompanied by a structural orthorhombic-to-orthorhombic transition for values of x up to 0.02 and by an orthorhombic-tetragonal-orthorhombic sequence where x = 0.04. Similar behaviour is also observed in the T/O solid solution in the La2-xNdxCuO4 SYStem (0 less-than-or-equal-to x less-than-or-equal-to 0. 3)