six specimens of the Hg0.5Pb0.5Ba2Ca2Cu3-y𝑁𝑖𝑦O8+δ (y=0.2,0.4,0.6,0.8,1.0)
superconducting compound were prepared by solid state reaction method, with sintering
temperature equal to 1123K for 24 hours. The electrical resistivity was examined by the four
probe technique, It was found that all the specimens have metallic behavior and increasing the
critical temperature with increasing nickel concentration. The optimum critical temperature Tc
was found equal to 137.5 K when the value of nickel concentration y=0.8. The structural of all
the specimens studied by using XRD analysis, this examination showed the crystal structure of
the specimens is polycrystalline with tetragonal structure. The volume fraction of high phase
Hg0.5Pb0.5Ba2Ca2Cu3-y𝑁𝑖𝑦O8+δ superconducting (Hg-1223 phase) increase up to 81.737% by
increasing Ni concentration for y=0.8, The increasing in nickel concentration causes due to
increase the high-phase 1223 and increment of c parameter.