PHASE-EQUILIBRIA IN ELECTROCHEMICALLY OXIDIZED LA2CUO4- TRANSPORT MEASUREMENTS VERSUS CHEMICAL-ANALYSIS(DELTA )

A comparative study of physical and chemical methods for the analysis of the number and identity of holes in electrochemically oxidized La2C uO4+delta is reported. A combination of TGA and iodometric chemical an alyses shows the existence of two species with different oxidation pot entials. Susceptibility and resistivity measurements show the existenc e of at least two segregated superconducting phases, while Seebeck mea surements shows a large change in the number of carriers for a constan t value of delta; this atypical behavior is consistent though with the chemical data and implies the existence of a phase equilibrium within the oxide.