In comparison to the Y1-xPrxBa2Cu3O7-delta (Y/Pr-123) system the influ
ence of the substitution of Pr for Y on the structural and superconduc
ting properties of the Y1-xPrxBa2Cu4O8 (Y/Pr-124) system was investiga
ted. Among the different reaction procedures for the synthesis at ambi
ent 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/P
r-124 with a critical Pr concentration x(cr) of 0.75 which is higher t
han that of 0.56 for Y/Pr-123. The normal-state behavior of the Y/Pr-1
24 samples could be described by a Curie-Weibeta law, yielding effecti
ve 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 the
ta was found to be positive for the superconducting and negative for t
he normal samples, whereas in Y/Pr-123 theta was always negative.