Superconducting water derivatives of Sr2Can−1CunO2+2n-δ (n = 2–4) high-Tc superconductors

• Novel water-derivative phases with Tc values exceeding 100 K.
• Topotactic water-intercalation process was occurred by simple annealing process.
• The crystal structure and superconductivity were studied.
• Novel water phases have same Tc as parent materials.
• The thickness of the non-superconducting blocking block has no effect on the superconducting properties.

We prepared two new phases of high-Tc superconductors with water molecules as the main constituents of the charge-reservoir block and refined the synthesis method for another phase. These water-containing phases form from high-pressure-synthesized Sr2Can−1CunO2+2n±δ or 0(Sr)2(n−1)n (n = 2–4) superconducting phases through a topotactic water-intercalation process when the parent phases are exposed to open air at 80 °C. Upon the water intercalation the body-centered unit cell of the parent phase is elongated along the c-axis direction by ∼6.2 Å. Despite the elongated unit cell the Tc value is not changed upon the water intercalation. The water-based H-m(Sr)2(n−1)n copper-oxide superconductors are new exotic members of the yet tiny family of superconductors with Tc values higher than 100 K.