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YBa_2Cu_(3-x)Nb_xO_(7-y) superconductors have been prepared. XRD shows that the system remains orthorhombic for all composition. Substitution of Nb~(5+) for Cu~(2+) occurs in the Cu(2) sites. The introduction of the Nb~(5+) ions produces some extra free-electrons. These electrons recombine with the carriers of the system. It makes the mobility and the Hall number of YBa_2Cu_(3-x)Nb_xO_(7-y) decrease and also result in a depression in Tc.
XRD shows that the system remains orthorhombic for all composition. Substitution of Nb ~ (5+) for Cu ~ (2+) occurs in the Cu (2) These makes the mobility and the Hall number of YBa_2Cu_ (3-x) Nb_xO_ (7-y ) decrease and also result in a depression in Tc.