A novel synthesis route to the mercury-containing superconductor HgBa2CaCu2O6+δ partly based on the sol–gel technique

Abstract

A sol–gel-based preparation route of precursors to be used in the synthesis of the high-T_c superconductor HgBa₂CaCu₂O_6+δ(Hg-1212) has been investigated. The samples were synthesized by reacting the precursor ‘Ba₂CaCu₂O_5+δ’, made from acetate-tartrate solutions containing appropriate amounts of Ba, Ca and Cu ions, and HgO in closed ampoules at 630–730 °C and yielded the 1212 phase as the major phase together with the starting precursor and Hg(I). The advantages of this method are that the impurity CaHgO₂ did not form and that the finegrained powders reacted only slightly with the silica tubes. The onset superconducting transition temperatures were 111 and 127 K, for the as-synthesized and oxygen-treated samples, respectively.