Thermoelectric power studies of a Nd1.82−xSrxCe0.18CuOy superconducting system (abstract) : 38th Annual Conference on Magnetism and Magnetic Materials

1089-7550

AIP Digital Archive

Physics

We have reported recently on the revival of superconductivity in Nd1.82Ce0.18CuOy by doping with a divalent alkaline earth element. The doped superconductor Nd1.82−xSrxCe0.18CuOy has a Nd2CuO4 (T'-type) structure. This system possesses a normal state metallic resistivity [ρ(T)] in polycrystalline form. The ρ(T) versus temperature (T) plots are, in general, linear. We report here the results of our studies of ρ(T) and thermopower S(T) and their dependence on the lattice oxygen content (y) that is a function of the Sr-content x. The dρ(T)/dT improves and then deteriorates with an increase in y. However, the thermopower behavior is a more complicated function of y (or x) and its results indicate that the majority of the charge carriers are electronlike. The thermopower (in absolute value) of the superconducting Nd1.73Sr0.09Ce0.18CuO3.97 compound gradually decreases from 250 to 150 K, remains almost constant from 150 to 75 K, decreases very fast below 75 K, and shows negative dS/dT. The overall feature of the S vs T plot suggests that the main contribution to S is from diffusion. Unlike reduced Nd1.82Ce0.18CuO4.01 and other electron-doped superconductors, we have not observed a peak near the transition temperature (Tc) on the higher temperature side of the S vs T plot of the present sample. An attempt is made to explain the salient features of the thermopower.

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