SYNTHESIS OF THE HIGH-TEMPERATURE SUPERCONDUCTORS HGBA2CACU2O6+DELTA AND HGBA2CA2CU3O8+DELTA

The newly-discovered homologous series HgBa2Can-1CunO2n+2+delta [Hg-12(n-1)n] with n=1, 2, 3,... possesses the highest superconducting transition-temperature (T(c)) to date. Unfortunately, because of the complexity of its compound chemistry. it remains a challenge to prepare samples with pure or nearly-pure Hg-12(n-1)n for both scientific and applied studies. In the present investigation, we report the successful development of a controlled vapor/solid reaction process for the synthesis of samples with up to 75 to 90% Hg-1212 and 65 to 75% Hg-1223 by volume, which display sharp superconducting transitions up to 135 K. Detailed steps of the process are presented and discussed.