PHASE-SEPARATION IN LA2CUO4-TRANSPORT MEASUREMENTS(DELTA BY ELECTRICAL)

The dc conductivity and the high-frequency capacitance of a La2CuO4+de lta Single crystal are determined by impedance spectroscopy in the fre quency range 20 Hz to 1 MHz at liquid helium temperature. Using isochr onal annealing, the effect of the phase separation on these quantitite s is studied for E parallel and perpendicular to the CuO2 planes as we ll as for different oxygen doping levels, delta, of the sample. The re sults are consistent with the model of a diffusion-controlled formatio n of a metallic-and below T-c superconducting-percolation network in a n insulating background.