Effect of Pr on electron band spectrum of YBa2Cu3Oy: study by thermopower data analysis

The temperature dependences of the thermopower, S(T) of Y_1−xPr_xBa₂Cu₃O_y (0≤x≤0.6) have been measured and analyzed within a phenomenological model of electron transport in the case of a narrow conductive band. The band spectrum parameters have been estimated by a quantitative comparison of the experimental and calculated S(T) curves. It was revealed that an increase of the Pr content results in remarkable broadening of the conductive band and a strong localization of the states. This can be considered as the main reason for T_c depression. The effect of Pr on the band filling is very slight that makes it possible to conclude a valence of Pr to be close to 3+. The Pr influence on superconducting properties of YBa₂Cu₃O_y cannot be described in the terms of hole-filling effect.