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Barium titanate nanoparticles were synthesized via a low temperature sol-gel technique using acetylacetone as a chelating agent. The X-ray diffraction pattern confirmed the formation of tetragonal perovskite structure of the material. The average crystallite size was found to be 49 nm using the Debye-Scherrer method. The Williamson–Hall plot was drawn for evaluating the micro-strain and crystallite size. Raman spectroscopic features typical for the tetragonal phase were identified for Barium titanate powder. In addition to these, an absorption band edge and an optical bandgap were found to be of 406 nm and 3.14 eV respectively. Barium titanate displays polychromatic luminescent peaks in UV -visible regions and it was attributed to the near-band-edge transition and defect states in the optical band gap of the perovskite structure. [ABSTRACT FROM AUTHOR]

A comparative investigation of the structural, optical, and magnetic properties of NiFe 2 O 4 (NFO) and ZnFe 2 O 4 (ZFO) spinel nanoparticles were synthesized by microwave combustion method. X-ray diffraction (XRD) showed that the ZFO spinel nanoparticles formed a cubic structure, but the NFO spinel nanoparticles formed with additional Fe 2 O 3 in them. The average crystallite size was observed to be in the range 16–20 nm. X-ray photoelectron spectroscopy (XPS) peak areas are often used to quantify the elemental compositions and oxidizing states of NFO and ZFO spinel surfaces. The appearance of FT-IR bands at around 548, 514 and 649 cm−1 were correlated to the Fe–O and Zn/Ni–O stretching modes of cubic NFO and ZFO structure. The direct band gap estimated using Kubelka–Munk (K–M) method to obtain by the NFO is 3.35 eV and ZFO is 2.13 eV respectively. The surface morphology revealed nanosized crystalline grains with agglomerate separated particles that are like spherical/non-spherical forms and fused grain boundaries. Magnetic measurements of NFO and ZFO spinel nanoparticles showed ferromagnetic behavior at room temperature. [ABSTRACT FROM AUTHOR]