Attempts to fabricate thick HgPb1223 superconducting films on silver

Abstract

The influence of the silver interface on the formation and growth of Hg 0.8Pb 0.2Ba 2Ca 2Cu 3O y (HgPb1223) superconductor was studied using dip-coated films. The formation of even small amounts of BaCO 3 or (Ba,Ca)PbO 4 during the heat treatment of dip-coated PbBaCaCuO precursor films inhibits their conversion to HgPb1223 in the following reaction with mercury. The heat treated precursor films were reacted in sealed tubes using CaHgO 2 as the mercury source. The temperature window for the processing of thick HgPb1223 films on silver is very narrow due to the lowering of melting temperature of silver to 765°C after extensive amalgamation during the reaction. The HgPb1223 films reacted at 2–3°C below the melting temperature exhibited optimum superconducting transition temperature of 135 K. The silver interface was shown to have a positive influence in lowering the reaction temperature and promoting grain growth. The superconducting layer at the silver interface had superior texture and magnetization hysteresis compared to that of the surface.