High-temperature resistivity of RBa2Cu3O7-y, where R=La, Pr, Nd, Sm, Eu, Dy, Ho, Er, and Tm

The electrical resistivity of RBa2Cu3O7-y, where R=La, Pr, Nd, Eu, Dy, Ho, Er, Sm, and Tm has been measured from room temperature up to 900 K. No essential difference in the transport properties was found except for LaBa2Cu3O7-y and PrBa2Cu3O7-y which shows an anomaly in the electrical resistivity. SmBa2Cu3O7-y samples with various oxygen contents are studied in detail. Metallic behavior and linear temperature dependence of have been found for SmBa2Cu3O7-y with 0<y<0.227. The linear temperature dependence of implies weak electron-phonon coupling, which suggests that other mechanisms for high-Tc superconductivity are needed.