Thermodynamic fluctuations and the thermoelectric coefficient in (Bi1.6Pb0.4)Sr2Ca3( CU1-xAgx) 4O12+δ superconductors

We present a study of the thermoelectric coefficient L(T) of polycrystalline silver doped (Bi1.6Pb0.4)Sr2Ca3(Cu1-xAgx)(4)O12+delta samples. L(T) relates the thermopower S(T) with electrical conductivity, sigma(T), and gives an indication of the influence of the order parameter fluctuations (OPF) on S(T) in the mean field region (MFR). The results of L(T) indicate that the critical behavior of S(T) above the superconducting transition is driven essentially by sigma(T). These results suggest that, in the MFR, L(T) is not affected by thermodynamic fluctuations of the superconducting order parameter (OPF). The OFF effects show a bidimensional character in the entire MFR, which is not affected by Ag doping. For low Ag concentrations, the experimental data Delta sigma/sigma(B) fit well to the Lawrence-Doniach model for layered superconductors in the MFR. Furthermore, the behavior of Delta L is nearly temperature independent.