Phase separation in La2CuO4+y ceramics probed by dielectric measurements

The low-frequency (102-105Hz) dielectric properties and dc resistivity of oxygen-doped La2CuO4+y ceramic samples were investigated as a function of temperature (23-300K). The as-prepared sample featuring phase separation shows very high dielectric constant ε′>105 above 150K, which was found to originate from the hopping motion of localized holes. Below 150K, the relaxation process due to the condensation of the holes can be observed in the dielectric spectra. When the sample was annealed at different temperatures in reduced atmosphere to tune the oxygen content, the phase separation disappears accompanied by the absence of the relaxation in the annealed sample. Our results give strong support to the phase separation model and evidence the inhomogeneous distribution of holes in the oxygen-doped La2CuO4+y ceramic samples investigated.