Superconducting and Nonsuperconducting Ca-Free Single Crystals of Pb2Sr2RCu3O8 (R = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Y): Effect of Cation Vacancies and the Metal/Insulator Transition

Ca-free single crystal and polycrystalline samples of Pb2Sr2RCu3O8 have been prepared by a PbO/NaCl flux growth method and a fast solid state reaction, respectively. The electronic character of the single crystals of this series can be roughly categorized into three groups: insulating (no carrier doping in the CuO2 planes) for R = La, Ce, Pr, and Nd, semiconducting for R = Sm, Eu, Gd, and Tb, and poorly metallic for R = Dy, Ho, and Y. Crystals …