Thallium Barium Calcium Copper Oxide

Thallium barium calcium copper oxide, or TBCCO (pronounced "tibco"), is a family of high-temperature superconductors having the generalized chemical formula Tl_''m'' Ba₂ Ca_''n''−1 Cu_''n'' O_{2''n''+''m''+2}.

Tl₂Ba₂Ca₂Cu₃O₁₀ (TBCCO-2223) was discovered in Prof. Allen M. Hermann's laboratory in the physics department of the University of Arkansas in October 1987 by the post-doctoral researcher Zhengzhi Sheng and Prof. Hermann. The bulk superconductivity in this material was confirmed by observations of magnetic flux expulsion and flux trapping signals (under zero field cooled and field cooled conditions) with a SQUID magnetometer in the superconductor laboratory of Timir Datta in the University of South Carolina. Allen Hermann announced his discovery and the critical temperature of 127 K, in Houston, Texas at the World Congress on Superconductivity organized by Paul Chu in February 1988.

The first series of the Tl-based superconductor containing one Tl–O layer has the general formula TlBa₂Ca_''n''-1Cu_''n''O_2''n''+3, whereas the second series containing two Tl–O layers has a formula of Tl₂Ba₂Ca_''n''-1Cu_''n''O_2''n''+4 with ''n'' =1, 2 and 3. In the structure of Tl₂Ba₂CuO₆ (Tl-2201), there is one CuO₂ layer with the stacking sequence (Tl–O) (Tl–O) (Ba–O) (Cu–O) (Ba–O) (Tl–O) (Tl–O). In Tl₂Ba₂CaCu₂O₈ (Tl-2212), there are two Cu–O layers with a Ca layer in between. Similar to the Tl₂Ba₂CuO₆ structure, Tl–O layers are present outside the Ba–O layers. In Tl₂Ba₂Ca₂Cu₃O₁₀ (Tl-2223), there are three CuO2 layers enclosing Ca layers between each of these. In Tl-based superconductors, ''T''_c is found to increase with the increase in CuO₂ layers. However, the value of ''T''_c decreases after four CuO₂ layers in TlBa₂Ca_''n''-1Cu_''n''O_2''n''+3, and in the Tl₂Ba₂Ca_''n''-1Cu_''n''O_2''n''+4 compound, it decreases after three CuO₂ layers.

See also

* Cuprate superconductors
* Bismuth strontium calcium copper oxide
* Yttrium barium copper oxide
* Lanthanum barium copper oxide

References

*''Copper Oxide Superconductors:, by Charles P. Poole, Timir Datta, Horacio A. Farach, John Wiley & Sons, 1988, ''
*''Superconductivity: Its historical Roots and Development from Mercury to the Ceramic Oxides, by Per Fridtjof Dahl, AIP, New York, 1st ed. 1992, ''

External links

Thallium-based high-temperature superconductors

High-temperature superconductors
Thallium compounds
Barium compounds
Calcium compounds
Copper(II) compounds
Oxides

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