Synthesis and characterization of single crystals of the superconductors Hg{sub 0.8}Bi{sub 0.2}Ba{sub 2}Ca{sub {ital n}{minus}1}Cu{sub {ital n}}O{sub 2{ital n}+2+{delta}} ({ital n}=2,3)
- Laboratoire CRISMAT, ISMRA et Universite de Caen, URA 1318 associee au CNRS, Boulevard du Marechal Juin, 14050 Caen Cedex (France)
Single crystals of the 1212 ({ital n}=2) and 1223 ({ital n}=3) mercury based cuprates have been grown using Bi{sub 2}O{sub 3} as a flux during the growth. The bismuth cations act as stabilizers of the structures which do not require the use of a dry box or high pressure. Electron microscopy and coupled energy dispersive spectroscopy analyses evidence the regularity of the 1212 and 1223 structures with a mercury layer of composition close to Hg{sub 0.8}Bi{sub 0.2}. Moreover the structural refinements based on x-ray-diffraction data of these crystals, show at the level of the [(Hg,Bi)O{sub {delta}}] layer a splitting of the oxygen site around the position (1/21/20). These as-grown superconducting crystals exhibit critical temperatures of 121 and 130 K for 1212 and 1223, respectively. The irreversibility lines (IL) and fishtail lines (FL) of these crystals are compared to those of (Hg,Bi)-1201 crystals and grain aligned Hg-1223 ceramics. These data show that the Hg{sub 0.8}Bi{sub 0.2}-1223 IL and FL lie above that of Hg{sub 0.8}Bi{sub 0.2}-1212. This suggests that the anisotropy of 1223 is smaller than that of 1212. The similarity of the FL{close_quote}s location of isostructural Tl-1223 and Hg{sub 0.8}Bi{sub 0.2}-1223 illustrates the role of the structure on the superconducting properties. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 399838
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 54, Issue 22; Other Information: PBD: Dec 1996
- Country of Publication:
- United States
- Language:
- English
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