Physical Properties of Mn2O3 Nanoparticles Synthesized by Co-precipitation Method at Different pH Values

Mn2O3 nanoparticles were synthesized at different pH values ranging from 10 to 13 by co-precipitation technique. The characterization of all samples were completed by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), ultraviolet-absorption spectroscopy (UV), Raman spectroscopy, and M-H loop measurements. The XRD spectra show that the structure of Mn2O3 is cubic, and the lattice parameter a decreases as pH increases. Crystalline size, determined from TEM and XRD analyses, decreases as pH increases. TGA curves show that a mass loss is significantly affected as pH increases, indicating the decomposition of organic species besides the oxidation of Mn2O3 to Mn3O4. FTIR spectra indicate that the absorption peaks at 593.73 and 519.09 cm(-11) referred to the stretching vibration of Mn-O and Mn-O-Mn bonds during the synthesis of Mn2O3 nanoparticles. UV-visible spectroscopy is measured in the range 250-800 nm and showed a deviation to the lower wavelength in addition to an increase in the band-gap energy (E-g) values from 1.012 to 1.370 eV is obtained. Raman spectra shows a slight deviation to the left which is conversely proportional to the crystalline size. M-H loops for the prepared samples were measured and the results of retentivity (M-s) and coercivity (H-c) were discussed.