ON CORRELATION BETWEEN THE T-C VALUE AND CONDUCTION-BAND PARAMETERS ESTIMATED BY THERMOPOWER DATA-ANALYSIS IN YBA2-XLAXCU3OY

The temperature dependences of the resistivity and thermopower for a s eries of YBa2-xLaxCu3Oy (0 less than or equal to x less than or equal to 0.5) ceramic samples have been measured. The results obtained have been analyzed on the basis of a narrow-band model. The effective bandw idth estimated in the framework of this model depends non-monotonicall y on the La content correlating with a non-monotonic behavior of both the orthorhombic distortion and critical temperature. The conclusion a bout: the determinant effect of disordering of the oxygen sublattice o n the band spectrum parameters and superconducting properties of the Y Ba2Cu3Oy system in the case of different cation substitutions was made . (C) 1997 Academic Press Limited.