Physical Properties of Mn{sub 2}O{sub 3} Nanoparticles Synthesized by Co-precipitation Method at Different pH Values
Mn{sub 2}O{sub 3} 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 Mn{sub 2}O{sub 3} 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 Mn{sub 2}O{sub 3} to Mn{sub 3}O{sub 4}. FTIR spectra indicate that the absorption peaks at 593.73 and 519.09 cm{sup − 11} referred to the stretching vibration of Mn–O and Mn–O–Mn bonds during the synthesis of Mn{sub 2}O{sub 3} 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{sub 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{sub s}) and coercivity (H{sub c}) were discussed.