STRUCTURAL CHARACTERIZATION OF ELECTROCHEMICALLY OXIDIZED LA2CUO4-GELMETHOD(DELTA PARTICLES PREPARED BY A SOL)

The structure of powder samples of electrochemically oxidized La2CuO4delta was studied using X-ray powder diffraction. The base La2CuO4 mat erial was prepared by a sol-gel method that allowed control of the mea n particle size by calcining at different temperatures, The results sh ow that the structure of die electrochemically oxidized samples is ver y sensitive to the synthesis method, particularly the calcination temp erature, T-cal. The refined lattice parameters b and c, the unit cell volume V, and the orthorhombicity of the oxidized samples are found to increase considerably when T-cal decreases. These variations indicate an increase in the quantity of interstitial oxygen in the samples cal cined at lower temperatures with respect to the interstitial oxygen pr esents in ceramic samples, Particle size distributions were determined by transmission electron microscopy. A decrease in the mean particle size when T-cal decreases was observed. (C) 1997 Academic Press.