A New Potassium Intercalation Compound of 3R-Nb1.1S2 and its Superconducting Hydrated Derivative Synthesized via Soft Chemistry Strategy

A new polymorph of potassium intercalation compound of 3R-Nb1.1S2 with chemical composition K0.77Nb1.1S2 was synthesized for the first time by a facile solution-phase method. Its structure was comprehensively characterized by powder XRD and high-resolution TEM. Furthermore, its hydrated derivatives KxNb1.1S2• yH2O were synthesized via soft chemistry strategy using etching agents of ethanol, water and an I2/CH3CN solution, respectively. Superconducting transition at 4.0 K was observed for the product with the doping content x=0.12. While superconductivity disappeared in products KxNb1.1S2• yH2O (x=0.48 and 0.35) which displayed a metal-to-semiconductor transition at low temperature. In addition, the XPS analysis revealed an upward shift in the Fermi level in K0.12Nb1.1S2• yH2O compared with the host or K0.77Nb1.1S2.