Ql. Xu et al., THE SYNTHESIS AND THERMAL-STABILITY OF SUPERCONDUCTING HGBA2CACU2O6+DELTA, Superconductor science and technology, 7(11), 1994, pp. 828-831
HgBa2CaCu2O6+delta has been synthesized through a two-step route, via
a precursor but under controlled Hg vapour pressure during the second
step. A calculated excess quantity of HgO was put along the precursor,
whereon the latter reacted with a stoichiometric amount of the former
. Annealing raised the superconduction critical temperature from 97 to
127 K, according to susceptibility measurements. Correspondingly, the
lattice parameters also increased. Microwave non-resonant absorption
experiments indicated a minute presence of Hg-1223. The thermal stabil
ity of Hg-1212 was studied with the help of thermogravity, differentia
l thermal analysis, mass spectroscopy, and x-ray diffractometry. Decom
position became significant above 600 degrees C, but the out-diffusion
followed by evaporation of Hg proceeded more slowly; the enthalpies o
f these two processes were approximately 43 and 130 kJ mol(-1).