Sodium cobaltates: crystal growth, structure, thermoelectricity, and superconductivity

A systematic study of growing NaxCoO2 (x=0.55–1.00) and NaxCoO2yH2O (x=0.26–0.42, y=1.3) single crystals has been performed to determine phase stability and the effect of hydration on the structural and magnetic properties of this system. Our experiments demonstrate that nearly pure α- (x=0.90–1.00) and α′- (x=0.75) phase of NaxCoO2crystals could be obtained using the optical floating zone method, while other phases with lower sodium content of