Intercalation of HgI2 into high-T(c) superconducting Bi1.85Pb0.35Sr1.9Ca2.1Cu3.1O(10+δ) (Bi2223) compound is achieved by a stepwise reaction technique in which the iodine intercalate is used as a secondary host material. While the vapor transport reaction is ineffective in intercalating mercuric salts directly into Pb-doped or single crystalline Bi-based cuprates, the present stepwise reaction method can provide a useful way of intercalating larger molecules into Bi2O2 double layers of Bi-based cuprates. According to Hg L(III)-edge extended X-ray absorption fine structure analyses, it is found that the intercalated mercuric iodide is stabilized as a linear molecule with additional free iodine species in the interlayer space of Bi2223. Taking into account the fact that no free iodine can be found in the HgI2 intercalated Bi2Sr2CaCu2O(8+δ) polycrystal prepared by the direct intercalation method; the present experimental finding indicates that the intracrystalline structure of mercuric iodides in Bi2O2 double layers can be modified by controlling the synthetic route. The linear geometry of intercalated mercuric iodide has been further confirmed by performing ex-situ X-ray diffraction measurements on the deintercalation products, which clarify that the partial deintercalation of mercuric iodide leads to the formation of an intermediate phase with a parallel orientation of HgI2 molecules with respect to the basal plane.
All Science Journal Classification (ASJC) codes
- Materials Chemistry