Synthesis and stability of HgRe1212 and HgRe1223 superconductors

Synthesis, phase stability, and superconducting properties of Re-doped Hg12 12 and 1223 superconductors are reported. HgRe1212 and HgRe1223 were synthe sized using a common synthesis protocol, using commercial BaCaCuO precursor powders with CaHgO2 as the external ag-source, Both starting composition a nd reaction temperature affect the phase stability and microstructure of th e final product. The resulting superconducting phase in both Hg0.8Re0.2Ba2C a1Cu2Oy and Hg0.8Re0.2Ba2Ca2Cu3Oy compositions was either HgRe1212 or HgRe1 223, depending on the reaction temperature. The microstructure and supercon ducting properties of HgRe1212 and HgRe1223 samples, however, depended to a large extent on the starting composition. Both the HgRe1212 and HgRe1223 s amples synthesized from a nominal composition of Hg0.8Re0.2Ba2Ca1Cu2Oy had larger and aligned colonies of grains whereas the samples synthesized a nom inal composition Hg0.8Re0.2Ba2Ca2Cu3Oy had smaller and randomly oriented gr ains. Measured T-c values for HgRe1212 and Hg1223 phases were 124h: and 134 K, respectively, Both microstructure and magnetization hysteresis measureme nts suggest that HgRe1212 is a better candidate for applications.