Strontium-based Mercury Cuprates with Perovskite-like Crystal Structures

Conditions of synthesis, structure, and temperatures of superconducting transitions of strontium-based mercury cuprates Hg—Sr—Me—Cu—O (Me = Ca, La, Ce, Sm, Ho) with perovskite-like crystal structure are described. The samples belong to two homological series: HgSr₂ (Ln, Ce)_n–1CunO_2n + _{2 + δ} with the Hg—O bond directed along <110> and (Hg, Cu) Sr₂Ln_n–1Cu_nO_{2n + 2 + δ} with the (Hg, Cu)—O bond directed along <100>. The variation of composition leads to rotation of the Hg—O bond along the hk0 direction and consequently to the increase of T_c from 28 K to 81 K. An anomaly of the resistivity was observed around 200 K for most of the investigated samples, independent of their content and phase composition.