Superconducting transition temperature (T c) as a function of oxygen concentration for hexagonal rubidium tungsten bronzes Rb x WO y with 2.80 ≤ y ≤ 3.07 and x = 0.19, 0.23, and 0.27 has been systematically investigated. Three regions corresponding to T c < 2 K (denoted as superconductivity suppressed region), T c∼ 3 K (superconductivity uniform region) and T c > 3 K (superconductivity enhanced region) were identified in T c–y phase diagram for Rb0.19WO y and Rb0.23WO y . No superconductivity enhanced region was observed for Rb0.27WO y . The superconductivity suppressed region shifts toward higher oxygen content as rubidium concentration increases. The local ordering of the intercalated rubidium atoms might be responsible for the intriguing T c–y phase diagram of RbxWOy.
Journal of Superconductivity and Novel Magnetism 20(3), pp.249-253