  A systematic investigation of La0.67Ca0.33MnO3 manganites has been
undertaken, mainly to understand the influence of varying crystallite size
(nanometer range) on electrical resistivity, magnetic susceptibility and
thermoelectric power. The materials were prepared by the sol-gel method of
sintering at four different temperatures between 800 and 1100 degrees C. The
samples were characterized by X-ray diffraction and data were analyzed using
Rietveld refinement. The metal-insulator transition temperatures (TP) are found
to increase with increasing sintering temperatures, while the magnetic
transition temperatures (TC) decrease. The electrical resistivity and
thermoelectric power data at low temperatures (T < TP) have been analyzed by
considering various scattering phenomena, while the high temperature (T > TP)
data were analyzed with Mott's small polaron hopping conduction mechanisms.
PACS Codes: 73.50.Lw, 75.47.Gk, 75.47.Lx
