Synthesis of High Temperature Superconductors HgBa₂CuO_4+y and HgBa₂Ca₂Cu₃O_8+y

High critical temperature superconductors of mercury- based system were synthesized under high pressure and high temperature. The resistance and ac magnetic susceptibility measurements for sample prepared at 25 kbar and 850°C for 1.5 h show that the sample without any added treatment was a mixture of Hg-1201 and Hg-1223. The T_c values of Hg-1223 phase and Hg-1201 phase are 132 and 98 K, respectively.