EFFECT OF SUBSTITUTION FOR CU IN BI2SR2CA(CU1-XMX)(2)O-Y (M=FE, CO) ON THERMOPOWER AND BAND SPECTRUM IN THE NORMAL-STATE

Systematic study of the thermopower, S, and resistivity, rho, for four series of Fe and Co doped Bi2Sr2CaCu2Oy ceramic samples with differen t oxygen content has been carried out. By means of analysis of the obt ained results on the basis of a narrow-band model, the main parameters of the band spectrum in the normal state have been determined. The co ncentration dependences of all parameters defined both experimentally and by calculations have a critical point of dopant content (x(c)-0.08 and 0.06 for Fe and Co doped samples, respectively). This fact sugges ts the type of substitution to change after x(c). We have also conclud ed that annealing in oxygen-deficit atmosphere and doping by Fe or Co affect oxygen atoms located in different positions.