Hole doping into Co-12s2 copper oxides with s fluorite-structured layers between CuO2 planespiezolaminated composite plate

National Taiwan University Dept Mech EngnFjellvag, H.H.FjellvagMoritaa, Y.Y.MoritaaNagai, T.T.NagaiLee, J.M.J.M.LeeChen, J.M.J.M.ChenLiu, R.S.R.S.LiuHauback, B.C.B.C.HaubackAwana, V.P.S.V.P.S.AwanaMatsui, Y.Y.MatsuiYamauchi, H.H.YamauchiKarppinen, M.M.Karppinen2006-11-152018-07-102006-11-152018-07-102006http://ntur.lib.ntu.edu.tw//handle/246246/2006111501275479In this work, the ﬁrst three members (s ¼ 1, 2, 3) of the Co-12s2 homologous series of multi-layered copper oxides are gradually doped with holes through high-pressure oxygenation (HPO). The phases differ from each other only by thickness of the ﬂuorite-structured layer block, (Ce,Y,Ca)–[O2–(Ce,Y)]s1, between two identical CuO2 planes. High-resolution transmission-electron microscopy (HRTEM) and electron diffraction (ED) analyses together with both synchrotron X-ray and neutron powder diffraction data, reveal that as a consequence of HPO the charge-reservoir CoO4-tetrahedra chains get broken and the lattice symmetry of the Co-12s2 phases changes from orthorhombic to tetragonal. Oxygen contents are analyzed for the samples with wet-chemical and thermogravimetric techniques. The valence state of copper in the CuO2 plane is determined from Cu L-edge X-ray absorption near-edge structure (XANES) spectra to be compared with the values estimated through bond-valence-sum (BVS) calculations from the crystal structure data. The positive charge induced by oxygen loading (or aliovalent CaII-for-YIII substitution in CoSr2YCu2O7+d) is found not to be completely accommodated in the CuO2 planes but be rather effectively trapped at the charge-reservoir Co atoms. Superconductivity appears in the Co-1212 (CoSr2YCu2O7+d) samples with the copper valence of 2.13 or higher, whereas in the Co-1222 (CoSr2(Ce0.25Y0.75)2Cu2O9+d) and Co- 1232 (CoSr2(Ce0.67Y0.33)3Cu2O11+d) samples Cu valence does not increase high enough to induce superconductivity.application/pdf841740 bytesapplication/pdfzh-TWMulti-layered copper oxidesFluorite-structured layersCo-12s2 homologous seriesCrystal structureOxygen contentHole-dopingCu valenceXANES spectroscopySuperconductivityHole doping into Co-12s2 copper oxides with s fluorite-structured layers between CuO2 planespiezolaminated composite platejournal articlehttp://ntur.lib.ntu.edu.tw/bitstream/246246/2006111501275479/1/1495.pdf