Synthesis and stability of HgRel212 and HgRel223 superconductors

Synthesis, phase stability, and superconducting properties of Re-doped Hgl212 and 1223 superconductors are reported. HgRel212 and HgRel223 were synthesized using a common synthesis protocol, using commercial BaCaCuO precursor powders with CaHgO2 as the external Hg-source. Both starting composition and reaction temperature affect the phase stability and microstructure of the final product The resulting superconducting phase in both HgogReojBaîCa UjO, and Hg08Re02Ba2Ca2Cu3Oy compositions was either HgRel212 or HgRel223, depending on the reaction temperature. The microstructure and superconducting properties of HgRel212 and HgRel223 samples, however, depended to a large extent on the starting composition. Both the HgRel212 and HgRel223 samples synthesized from a nominal composition of HgajReojBajCajC Oy had larger and aligned colonies of grains whereas the samples synthesized a nominal composition Hgo. sRe02Ba2Ca2Cu3Oy had smaller and randomly oriented grains. Measured Tc values for HgRel212 and Hgl223 phases were 124K and 134K, respectively. Both microstructure and magnetization hysteresis measurements suggest that HgRcl212 is a better candidate for applications.