  We report a detailed study of structural and magnetic properties of the
pyrochlore-type (Bi2-xPrx)Ru2O7 series. Eleven compositions with 0 <= x <= 2
were prepared by solid state reaction at 1050 degrees C and found to form a
solid solution in the whole range of compositions. Structural refinements from
X-ray powder diffraction data by the Rietveld method show that the main
variation concerns the ruthenium site. Ru-O distances increase and the Ru-O-Ru
angle (bridging corner-sharing Ru-O octahedra) decreases with increasing
praseodymium content, in agreement with the metal-semiconductor transition
observed previously in this system. Magnetic measurements show that the
metallic Pauli paramagnetism of Ru in Bi2Ru2O7 evolves to a magnetism of
localized low spin moments coexisting with the magnetism of Pr3+ cations
moments. Strong magnetic correlations are present at high Pr content, as
illustrated by a N\'eel temperature of -224 K for Pr2Ru2O7. However no evidence
of a magnetic ordering was found, suggesting that the end compound Pr2Ru2O7 of
the series might stabilize a spin liquid phase.
