Ba. Scott et al., LAYER DEPENDENCE OF THE SUPERCONDUCTING TRANSITION-TEMPERATURE OF HGBA2CAN-1CUNO2N+2+DELTA, Physica. C, Superconductivity, 230(3-4), 1994, pp. 239-245
High-pressure methods have been used to synthesize multiphase composit
ions in the Hg-12{n-1}n homologous series. The phase assemblages were
examined by optical, electron diffraction and X-ray diffraction techni
ques, and their stoichiometries verified by electron microprobe. Trans
port and magnetic susceptibility measurements were combined with the r
esults of the phase analysis to establish superconducting transition t
emperatures for both as-prepared and O2- or Ar-annealed materials. It
was found that the transition temperature peaks at T(c) = 134 K for n
= 3 and then decreases abruptly for n > 4, reaching T(c) < 90 K for n
greater-than-or-equal-to 7.