The influence of the temperature treatment on the Nd2-xCexCuO4-y crystals surface

Superconductivity in the Nd2-xCexCuO4-y (NCCO) system can be obtained in a narrow range of the cationic and anionic stoichiometry. One possibility to enlarge this range is lowering oxygen concentration with preservation of th e T' structure. The surface morphology of Nd1.94Ce0.06CuO4-y after heat tre atment in a reducing atmosphere (argon) in the wide temperature range from 890 to 1120 degrees C was studied using atomic force and scanning electron microscopes. It was observed that the "as-grown" Nd1.94Ce0.06CuO4-y single crystals the surfaces are flat with steps about two lattices parameters whi le a high-temperature reduction process (T greater than or equal to 1080 de grees C) leads to a considerable deviation from the flatness. Elongated, re ctangular crystalline features of the height between 30 and 120 nm can be o bserved. EDAX investigations showed that the objects are Nd2-xCexCu1-zO4-y, with z approximate to 0.3. It should be noted that NCCO crystal encapsulat ed in polycrystalline material and annealed at the same temperature for 48 h did not show any decomposition effects. (C) 1999 Elsevier Science Ltd. Al l rights reserved.