Transformation in the structural and optical properties with the phase change from hematite (Fe2O3) to pure spinel structure in Mn-Zn nanoferrites

In present investigation, the effect of phase change, induced via sintering, from hematite (Fe2O3) to pure spinel structure on structural and optical properties in coprecipitated Mn0.4Zn0.6Fe2O4 nanoferrites has been studied. The Mn0.4Zn0.6Fe2O4 nanoparticles have been sintered at three temperatures 700 °C, 900 °C, and 1100 °C for 3 h. The presence of hematite (Fe2O3) phase in samples sintered at temperatures 700 °C and 900 °C has been observed from XRD. The crystallite size of the sintered samples has been found to increase on increasing the sintering temperature from 700 °C to 900 °C and then decrease for 1100 °C. Pure cubic spinel structure having single-phase has been obtained at 1100 °C. A cation distribution has also been proposed. Two absorption bands in the range 445 cm−1-473 cm−1, as well as 556 cm−1-582 cm−1, have been recognized in FTIR spectra and that indicates the formation of metal ion oxygen bond in spinel structure. With the rising sintering temperature, the peak position in the absorption spectra has been noticed to shift toward lesser wavelength, i.e., from 266 nm to 261.18 nm. The optical band gap shows shrinkage with the augmentation in the crystallite size on elevating the sintering temperature from 700 °C to 900 °C, while the optical band gap shows a broadening on raising the sintering temperature to 1100 °C. Photoluminescence study on the sintered samples has also been performed to examine the impurity levels and defects in samples. Stokes shift has been observed in all three samples.