J. Phys. IV France 7 (1997) C2-1233-C2-1234
X-Ray Absorption Spectroscopic Study of New High-Tc Superconducting Intercalation Compound of (HgX2)0,5Bi2Sr2CaCu2Oy (X = Br, I)J.-H. Choy and S.-J. Hwang
Department of Chemistry, Center for Molecular Catalysis, Seoul National University, Seoul 151-742, Korea
We have systematically performed X-ray absorption spectroscopic (XAS) studies on the new mercuric halide intercalated superconductors, (HgX2)0.5Bi2Sr2CaCu2Oy with X = Br and I, in order to investigate the electronic and crystal structures of these compounds. According to the I LI- and Br K-edge X-ray absorption near edge structure (XANES) spectroscopic analyses, it is found that a small amount of electron is transferred from the intercalant HgX2 to the host lattice, resulting in the negatively charged state of (HgX2)δ-. The Cu K-edge extended X-ray absorption fine structure (EXAFS) analysis reveals that the bond distance of (Cu-Oaxial) is slightly shortened upon intercalation, reflecting the oxidation of CuO2 layer, which is well consistent with the I LI- and Br K-edge XANES results. On the other hand, the present Hg LIII- edge EXAFS results indicate that the mercury is coordinated with two bromide or iodide ligands with bond length of 2.46 Å for the HgBr2-intercalate and 2.65 Å for the HgI2-one, respectively. This is the first example of linear molecular salt of HgX2 stabilized in the solid lattice.
© EDP Sciences 1997