Sintered samples of Nd1-xPrxBa2Cu3O72dwithx50, 0.05, 0.10, 0.15, 0.20, and 0.30 have been studied by neutron diffraction, x-ray diffraction, and resistivity measurements. Sample stoichiometry was carefully checked. Atomic distances within the unit cell and the oxygen content were shown to be almost independent of Pr doping. Bond valence sums (BVSs) were calculated from the neutron diffraction data assuming either a constant valence or a mixed valence for Cu and Pr ions. The planar Cu2 valence is independent of Pr doping and the chain Cu1 valence is roughly constant, while the hole concentration in the planes and chains decrease with increasing Pr doping for both BVS calculation methods. All together, this indicates that hole localization on the Nd(Pr) site is a main reason for the decrease of the hole concentration in the planes. A consistent relation between the hole concentration in the planes calculated from the constant valence method and the depression of the critical temperature is also obtained, both for Pr-doped Nd-123 and for Y(Pr)-123 studied previously.

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