The Mechanism of Surface Decomposition of Tl- and Hg-Containing Superconductors

The surface chemistry of various Tl- and Hg-containing superconducting oxides has been studied by high resolution transmission electron microscopy. The mechanism of surface decomposition of these materials is discussed. High chemical reactivity of the Tl-O and Hg-O layers seem to be the main course of the decomposition. It is proposed that a surface substitution of Tl and Hg may stabilise the structures without losing superconducting properties.