Crystal Structure of Tl2Ba2Ca2Cu3O10, a 125 K Superconductor

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Science  29 Apr 1988:
Vol. 240, Issue 4852, pp. 631-634
DOI: 10.1126/science.240.4852.631


There is now a new series of high-temperature superconductors that may be represented as (AIIIO)2A2IICan-1CunO2+2n where AIII is Bi or Tl, AII is Ba or Sr, and n is the number of Cu-O sheets stacked consecutively. There is a general trend toward higher transition temperatures as n increases. The highest n value for a bulk phase is three and is found when AIII is Tl. This compound, Tl2Ba2Ca2Cu3O10, has the highest transition temperature(∼125 K) of any presently known bulk superconductor. The structure of Tl2Ba2Ca2Cu3O10 has been determined from single-crystal x-ray diffraction data and is tetragonal, with a = 3.85 Å and c = 35.9 Å. No superstructure is observed, and the material is essentially twin-free. Electron microscopy in the Tl/Ba/Ca/Cu/O system has revealed intergrowths where n = 5; such regions may well be responsible for the superconducting onset behavior observed in this system at about 140 K.