Nh. Hur et al., SYNTHESIS AND CHARACTERIZATION OF A NEW MERCURY-BASED SUPERCONDUCTOR,HG0.5TL0.5BA2CA1-XSRXCU2O6+DELTA, Physica. C, Superconductivity, 231(1-2), 1994, pp. 4-8
A new mercury-based superconductor Hg0.5Tl0.5Ba2Ca1-xSrxCu2O6+delta (x
= 0.14, denoted as Hg,Tl-1212) was synthesized from the reaction of H
gO, Tl2O3, Ba2CuO3+x, and Ca1-xSrxCuO2. X-ray powder diffraction analy
sis showed that the thallium completely substitutes for the mercury si
tes in the rock-salt [HgO delta] layer. The as-synthesized Hg,Tl-1212
has a T-c of 122 K. Surprisingly the T-c decreased to about 100 K upon
annealing in an oxygen atmosphere at 350 degrees C for 8 h while the
argon annealing did not show any substantial change in T-c under the s
ame condition. The crystal symmetry was found to be tetragonal (P4/mmm
) with lattice parameters a = 3.8496(1) Angstrom and c = 12.6536(4) An
gstrom. The Hg,Tl-1212 is quite stable up to 450 degrees C. The intra-
critical current density of Hg,Tl-1212 is about twice larger than that
of HgBa2Ca1-xSrxCu2O(6+delta) (x = 0.14). The substitution of Tl for
Hg clearly stabilized the Hg,Tl-1212 phase as well as enhanced the pin
ning property.