Search for new superconductors by the Li-intercalation into layered perovskites

Synthesis and superconductivity of new Li-intercalated layered perovskites, LixSr2CuO2X2 (X = Cl, Br, I) and LixAB2M3O10 (A = K, Rb, Cs; B = Ca, Sr, Ba; M = Nb, Ta), are reviewed. Li-intercalation has been carried out by the electrochemical technique. First, layered cuprates LixSr2CuO2X2 show superconductivity with Tc = 8.0 K and 4.5 K for X = Br and I, respectively. However, no superconductivity appears for X = Cl. Next, we have succeeded in preparing new superconductors, LixCsSr2Nb3O10 with Tc = 5.5 K and LixRbSr2Nb3O10 with Tc = 6 K. In the layered tantalates of LixCsSr2Ta3O10, however, no superconductivity has been observed.