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Nanometer manganic oxide (Mn2O3) has been prepared by the chemical liquid homogeneous precipitation (CLHP) method. The size dependence of phonon Raman spectra in Mn2O3 nanocrystals has been investigated. Transmission electron micrographs and X-ray powder diffraction patterns show that the average particle sizes are in the range of 9 to 50 nm. From the Raman spectra patterns of the nanometer Mn2O3 particle, we determined the broadening of the Raman peak in the lower frequency region. This phenomenon was explained by a spatial correlation model. We also found that the intensities of the main Raman peak decrease with the decrease in the grain size of Mn2O3 nanocrystals.

Single-phase Bi 2 Sr 2 Ca 1−x Ce x Cu 2 O 8+y (x = 0-0.4) samples were prepared by a solid state reaction method. The thermoelectric power (TEP) of the system was measured, for the first time, in the liquid nitrogen temperature range. The TEP results are similar to those of high-T c superconductor systems doped with other rare earth elements or with different oxygen contents. Several two-band models are used and compared to judge which model is more suitable for describing the TEP behaviour of high-T c superconductors in the normal state.

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