NEUTRON POWDER DIFFRACTION STUDY OF PHASE-SEPARATION IN LA2CUO4+DELTA OXIDIZED IN KMNO4 SOLUTIONS

Three samples of superconducting La2CuO4+delta with delta values of 0.047, 0.073, and 0.132 were prepared by oxidizing La2CuO4 in aqueous solutions of KMnO4 at 50 degrees C. The samples with delta = 0.073 and 0.132 respectively contained 3 and 2 phases with different delta and T-c values as a result of phase separation on exposure to air at room temperature. The crystal structures of the La2CuO4+delta phases in the three samples were studied by time-of-flight neutron powder diffraction. We could successfully determine the lattice and structure parameters of the constituent phases as well as their mass fractions.