Electrochemical synthesis and characterization of La2CuO4+delta single crystals

An electrochemical oxidation technique was used to obtain bulk oxidized La2 CuO4+delta single crystals from the as-grown crystals. Samples were prepare d by galvanostatic oxidation with currents in the range 5-10 mu A and with different charging times. Some samples were annealed at 110 degrees C in fl owing oxygen. Small high-quality crystals were obtained from electrochemica lly oxidized larger crystals that contained microcracks, Transmission x-ray Laue photography and rocking curve measurements for several fundamental di ffraction peaks were used to confirm the crystal quality. The T-c and bulk magnetic properties of samples at different stages in the oxidation process are reported. After annealing at 110 degrees C, a 15 K transition was obse rved.