PREPARATION AND CHARACTERIZATION OF Y1-XPRXBA2CU4O8

In comparison to the Y1-xPrxBa2Cu3O7-delta (Y/Pr-123) system the influence of the substitution of Pr for Y on the structural and superconducting properties of the Y1-xPrxBa2Cu4O8 (Y/Pr-124) system was investigated. Among the different reaction procedures for the synthesis at ambient oxygen pressure a technique involving the crystallization from the quenched melt was employed for the first time. In analogy to the Y/Pr-123 system the Pr substitution leads to an increase of the unit-cell parameters and to a successive suppression of superconductivity in Y/Pr-124 with a critical Pr concentration x(cr) of 0.75 which is higher than that of 0.56 for Y/Pr-123. The normal-state behavior of the Y/Pr-124 samples could be described by a Curie-Weibeta law, yielding effective Pr moments of about 2.5 mu(B) that correspond to a Pr valence of 4+. Different from theY/Pr-123 system, the Curie-Weibeta temperature theta was found to be positive for the superconducting and negative for the normal samples, whereas in Y/Pr-123 theta was always negative.