Superconductivity of (R0.4Pr0.6)(0.5)Ca0.5Ba2Cu3O7-delta (R = La, Pr, Nd, Sm, Eu, Gd and Y) prepared under high pressure

The nearly single phase (R0.4Pr0.6)(0.5)Ca0.5Ba2Cu3O7-delta compounds (R = La, Pr, Nd, Sm, Eu, Gd and Y) with T-c about 100K were prepared under high pressure and high temperature using the cubic-anvil apparatus. The T-c is m uch higher than that of the traditional R-123 superconductors without dopin g Ca on the rare-earth site. For various rare earths with different ionic r adii, the (R0.4Pr0.6)(0.5)Ca0.5Ba2Cu3O7-delta compounds have almost the sam e critical temperature. This is different from the result of the ion-size e ffect of rare-earth ions in R1-xPrxBa2Cu3O7-delta compounds. Our results sh ow that Pr has the same properties as other rare earths in the 123-phase co mpounds due to the doping of Ca.