Variation of thermoelectric power with crystallite size of La0.67Sr0.33MnO3 manganites

Thermoelectric power (TEP) studies of La0.67Sr0.33MnO3 polycrystalline manganite material system having varying particle size have been undertaken. These materials were prepared by citrate based sol-gel route by sintering at four different temperatures and were later characterized by X-ray diffraction (XRD), scanning electron microscopy, electrical resistivity, AC susceptibility, etc., studies. The XRD data were analyzed by Rietveld refinement technique. Thermopower versus temperature plots are found to exhibit two peaks and an effort has been made to explain the significance of both of them. Finally, with a view to understand the conduction mechanism in these materials, TEP data in the low-temperature ferromagnetic metallic (T TP) regime were analyzed using electron-magnon scattering phenomenon, while that in the high-temperature insulating (T TP) region were analyzed by small polaron hopping model.