Charge Transfer–TcRelation in the Superconducting Intercalates IBi2Sr2CaCu2O

Soft Chemical Routes to Heterostructured High-Tc Superconducting Materials

“…35 Direct evidence of the oxidation of the host lattice upon intercalation can be obtained by Cu K-and Bi L III -edge XANES results, where a slight edge shift toward the high-energy side is discernible after intercalation. 31,33 This influence of intercalation on the host lattice was further confirmed from the Cu K-edge extended x-ray absorption fine structure (EXAFS) results, clarifying a significant shortening of (CuϪO) axial bond distances. 31 Based on this spectroscopic evidence of electron transfer between host and guest, the observed T c depression upon intercalation could also be explained by an increase in hole concentration in the CuO 2 layer, taking into account the fact that the Bi-based cuprate has an overdoped or optimally doped hole concentration, and therefore, an increase in hole density gives rise to a T c depression.…”

“…31,33 This influence of intercalation on the host lattice was further confirmed from the Cu K-edge extended x-ray absorption fine structure (EXAFS) results, clarifying a significant shortening of (CuϪO) axial bond distances. 31 Based on this spectroscopic evidence of electron transfer between host and guest, the observed T c depression upon intercalation could also be explained by an increase in hole concentration in the CuO 2 layer, taking into account the fact that the Bi-based cuprate has an overdoped or optimally doped hole concentration, and therefore, an increase in hole density gives rise to a T c depression. 36 In this context, the dissimilar T c shifts for the first-staged and second-staged intercalates can also be rationalized by a different amount of hole doping to the CuO 2 layer, which is surely dependent upon the iodine content.…”

“…32 However, it has been established that the interlayer iodine is stabilized as the triiodide (I 3 Ϫ ) ion, by performing micro-Raman scattering as well as I L Iedge x-ray absorption near-edge structure (XANES) spectroscopic experiments. 31,[33][34][35] In addition, the shift of Raman peaks corresponding to oxygen motion was also observed for the iodine intercalates, indicative of considerable interaction between the BiO layer and the iodine one. 35 Direct evidence of the oxidation of the host lattice upon intercalation can be obtained by Cu K-and Bi L III -edge XANES results, where a slight edge shift toward the high-energy side is discernible after intercalation.…”

“…In fact, x-ray photoelectron spectroscopic (XPS) analysis indicated that the intercalated iodine exhibits two kinds of oxidation states, I ␦Ϫ and I ϩVII , suggestive of electron transfer between host and guest. [29][30][31] The other XPS study on iodine intercalates with different oxygen contents demonstrated that most of the intercalated iodine is stabilized in the interlayer space with a negatively charged state, while a small concentration of highly oxidized periodate I ϩVII species is formed on the sample surface or grain boundary. 32 However, it has been established that the interlayer iodine is stabilized as the triiodide (I 3 Ϫ ) ion, by performing micro-Raman scattering as well as I L Iedge x-ray absorption near-edge structure (XANES) spectroscopic experiments.…”

Influence of Host Lattice on the Chemical Bonding Nature of Guest Species in High-Tc Superconducting I−Bi2Sr1.5-xLaxCa1.5Cu2Oy Nanohybrids

“…[17][18][19][20] The single phasic intercalates of iodine were obtained by heating the pristine polycrystals with an excess amount of guest molecules in an evacuated silica tube at 180°C for iodine. The formation of the first-staged iodine intercalates IBi 2 Sr 1.5-x La x Ca 1.5 Cu 2 O y was confirmed by powder X-ray diffraction (XRD) analyses.…”