SUPERCONDUCTING PROPERTIES OF (Y1-XPRX)BA2CU4O8 COMPOUNDS

(Y1-xPTx)Ba2Cu4O8 compounds with x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7 were synthesized using a high-pressure oxygen technique. The solubility limit x(s) in this compound system was found to be 0.7. In this composition range, (Y1-xPrx)Ba2Cu4O8 compounds have the YBa2Cu4O8(124) structure and the lattice parameters a, b and c increase with increasing Pr content x. The superconducting transition temperature T-c decreases monotonically with increasing x, and the critical content x(c), where superconductivity disappears, has been estimated to be 0.8. There is an obvious effect of Pr substitution on superconductivity, although the effect is smaller in the 124 system than that in the 123 system. X-ray diffraction results suggest that Pr is almost 3+ in this system. A model for the Pr substitution is suggested to make holes immobile to suppress superconductivity as the result of the hybridization of O 2p(x) with Pr 4f orbitals.