EFFECT OF PR ON ELECTRON BAND SPECTRUM OF YBA2CU3OY - STUDY BY THERMOPOWER DATA-ANALYSIS

The temperature dependences of the thermopower, S(T), of Y1-xPrxBa2Cu3 Oy (0 less than or equal to x less than or equal to 0.6) have been mea sured and analyzed within a phenomenological model of electron transpo rt in the case of a narrow conductive band. The band spectrum paramete rs have been estimated by a quantitative comparison of the experimenta l 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 ma in 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 c lose to 3(+). The Pr influence on superconducting properties of YBa2Cu 3Oy cannot be described in the terms of hole-filling effect.