Attempts to fabricate thick HgPb1223 superconducting films on silver

The influence of the silver interface on the formation and growth of Hg0.8P b0.2Ba2Ca2Cu3Oy (HgPb1223) superconductor was studied using dip-coated film s. The formation of even small amounts of BaCO3 or (Ba,Ca)PbO4 during the h eat treatment of dip-coated PbBaCaCuO precursor films inhibits their conver sion to HgPb1223 in the following reaction with mercury. The heat treated p recursor films were reacted in sealed tubes using CaHgO2 as the mercury sou rce. The temperature window for the processing of thick HgPb1223 films on s ilver is very narrow due to the lowering of melting temperature of silver t o 765 degrees C after extensive amalgamation during the reaction. The HgPb1 223 films reacted at 2-3 degrees C below the melting temperature exhibited optimum superconducting transition temperature of 135 K. The silver interfa ce was shown to have a positive influence in lowering the reaction temperat ure and promoting grain growth. The superconducting layer at the silver int erface had superior texture and magnetization hysteresis compared to that o f the surface. (C) 2000 Elsevier Science B.V. All rights reserved.