Chemical stabilization and high pressure synthesis of Ba-free Hg-based superconductors, (Hg,M)Sr2Ca(n-1)Cu(n)O(y)(n=1 to approximately 3)

A homologous series of new Hg-based HTSC compounds, (Hg,M)Sr2Ca(n - 1)Cu(n)P(y) with n = 1 to 3, have been synthesized. The stabilization of the pure phases have been accomplished by chemical doping of third elements such as M = Cr, Mo and Re. While the Hgl2O1(n = 1) phase was readily obtained in this way, it was necessary to simultaneously dope Y into the Ca site to stabilize the Hg1212(n = 2) phase. On the other hand, single-phase Y-free Hg1212(n = 2) and Hg1223 (n = 3) samples were synthesized only under a high pressure of 6 GPa. In sharp contrast to the Ba containing compounds, all the samples prepared in the present study have been quite stable during the synthesis and no deterioration in air has been observed after the preparation.