Barium titanate, BaTiO3 ceramic powders were prepared by mechanochemical synthesis and by the Pechini method. A powder mixture of BaO and TiO2 was treated in a planetary ball mill in an air atmosphere for up to 1 h, using zirconium oxide vial and zirconium oxide balls as the milling medium. After 60 min BaTiO3 phase was formed. In both ways BaTiO3 ceramics were sintered after 2 h on 1300 • C without pre-calcinations step. The heating rate was 10 • C min −1 . The formation of phase and crystal structure of BaTiO3 was approved by X-ray diffraction analysis and the Raman spectroscopy. The morphology and microstructure of obtained powders were examined by scanning electron microscopy method. Sharp phase transition from ferroelectric to paraelectric state was observed. The hysteresis loop is very well performed with regular sharp characteristic of ferroelectric materials.
Powders consisting of 44 Å Cd1−xMnxS (x = 0; 0.05; 0.1; 0.15; 0.3) quantum dots (QDs) were synthesized using the colloidal chemistry method and characterized by Raman scattering measurements. The dominant Raman line of the 44 Å Cd1−xMnxS QDs was at about 300 cm−1 showing asymmetric broadening for ω < 300 cm−1. A significant change in the intensity of the first harmonic for different x and excitation energies was noticed. Also, the second harmonic of confined Raman modes was experimentally observed. A theoretical model was used to calculate the relative contributions of the confined Raman scattering modes for the 44 Å CdS QDs and satisfactory agreement with experimental results was found.
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