Microsc. Microanal. Microstruct. 4, 41-50 (1993)
DOI: 10.1051/mmm:019930040104100

High resolution electron microscopy study of the high Tc superconductor Tl0.5Pb0.5Sr4Cu2CO3O7

Maryvonne Hervieu, Claude Michel, Marielle Huve, Christine Martin, Antoine Maignan et Bernard Raveau

Laboratoire CRISMAT-ISMRA, Université de Caen, Bd. du Maréchal Juin, 14050 Caen Cedex, France

Abstract
The structure and the microstructure of the new high Tc superconductor Tl0.5Pb0.5Sr4Cu2CO 3O7 have been studied by high resolution electron microscopy. The experimental images fit well with the calculated ones based on a structure built up from the intergrowth of a 1201-type slice [Tl0.5Pb 0.5Sr2CuCO5]1201∞ with a [Sr2CuCO3O2]∞ unit. The comparison of the calculated and experimental images with those of a 1223 structure, which exhibits similar cell parameters to those of Tl0.5Pb0.5Sr4Cu2CO3O7, shows that the oxycarbonate exhibits a characteristic contrast for some focus values which allows to differentiate the two structures. The investigation of numerous crystals attests of the high regularity of the stacking of the layers along c. One single type of defect was observed which suggests the possible existence of a new member [Tl0.5Pb0.5Sr2CuO5] [Sr2CuCO3O2]2 .

PACS
6166F - Inorganic compounds.
7472J - Other cuprates, including Tl and Hg-based cuprates.

Key words
Experimental study -- Crystal structure -- Microstructure -- High-Tc superconductors -- Electron microscopy -- High-resolution methods -- Crystal defects -- Thallium oxides -- Lead oxides -- Strontium oxides -- Copper oxides -- Carbonates -- Multi-element compounds -- Carbonates oxides -- Structure of liquids -- Structure of solids -- Crystallography -- Condensed matter physics -- Materials science -- Physics -- Superconductivity -- Condensed state physics -- Inorganic compounds -- Transition element compounds


© EDP Sciences 1993