Structure and Superconductivity in the (Er0.9-xRxCa0.1)Sr2(Cu2.7Mo0.3)Oz (R = Pr, Nd and Ho) System

Sr-based 123 compounds of (Er$_{0.9-x}$R$_{x}$Ca$_{0.1}$)Sr$_{2}$(Cu$_{2.7}$Mo$_{0.3}$)O$_{z}$ (R = Pr, Nd and Ho; 0 $\le$ {\it x} $\le$ 0.9) have been synthesized and examined for superconductivity. We find that T$_{c}$ decreases monotonically from around 43 K to 20 K as the R concentration increases from {\it x} = 0 to {\it x} = 0.6 for both R = Pr and R = Nd whereas there is no significant change in T$_{c}$ for R = Ho. Room-temperature thermoelectric power measurements reveal that the suppressions of T$_{c}$ by Pr and Nd doping are due to a decrease in the mobile hole concentration. The similarity between the T$_{c}$ suppressions by Pr and Nd doping at the same doping content indicates that the suppressions cannot be ascribed to hole filling or hole localization. The experimental results are discussed in connection with the rare-earth ion-size dependence of T$_{c}$ and the weakening of Pr-O hybridization in the Mo-doped Sr-based 123 system. KCI Citation Count: 4