The valence of Pr IN PrBa2Cu3O7−δ and the related compounds as determined by neutron powder diffraction

We performed the crystal structure analysis of PrxNd1−x(Ba1.9Nd0.1)Cu3O7−δ system from x = 0 to 1.0 by neutron powder diffraction. We are especially interested in the distances of M(2)–O(4) and M(2)–O(5) in order to reveal the effect of substitution of Nd by Pr, where M(2) indicates the site occupied by Nd/Pr and O(4) and O(5) are the oxygen sites in the CuO2 layer. As a result, both distances become anomalously smaller with increase of the Pr-contents. According to an estimation by the Bond-Valence-Sum of M(2), the valence of Pr ranges from +3.4 to +3.5.