Study of the optical properties of Zn doped Mn spinel ferrite nanocrystals shows multiple emission peaks in the visible range –a promising soft ferrite nanomaterial for deep blue LED

Abstract

Here, in this report, chemical co-precipitation method has been used for the synthesis of zinc doped manganese spinel ferrite nanocrystals, having the chemical formula of Mn0.5Zn0.5Fe2O4. The structural and morphological analysis have been carried out using X-ray diffraction (XRD) analysis and High Resolution Transmission Microscope (HRTEM). XRD analysis has revealed the formation of pure phase face centred cubic (FCC) spinel ferrite nanocrystals with the average size of 28 nm approximately. Electron Microscopic images show the spherical morphology of the prepared ferrite nanocrystals and the average size obtained from these observation matches well with that from XRD result. Further, Selected Area Diffraction Pattern (SAED) of the prepared nanocrystals gives the combined pattern of concentric rings and sharp bright spots over the rings, which indicates the polycrystalline nature of the sample. Again, elemental analysis of the nanocrystals has been studied by Energy dispersive X-ray spectroscopy (EDX). Ultraviolet–Visible (UV–Vis) spectroscopy measurement shows an absorption peak in the visible range at around 346 nm. From the absorption data, the optical band gap energy has been calculated using Tauc’s plot, which is found to be approximately 3.47 eV. Similarly, UV–Vis diffuse reflectance spectra (DRS) also provide almost the same band gap, following Kubelka–Munk function. Luminescence spectra gives three sharp emission peaks in the visible range at 409 nm, 430 nm and 460 nm of wavelength, on exciting the samples with 350 nm and the intensity of the peaks has been found to decrease on exciting again the sample with 380 nm and 400 nm respectively. In addition, Commission Internationale de L’Eclairage (CIE) diagram shows that this sample can act as a blue light emitting diode (LED). Vibrating Sample Magnetometer (VSM) shows the superparamagnetic nature of the prepared sample and hence, Mn0.5Zn0.5Fe2O4 nanocrystals can be used as a soft ferrite substance and it’s interesting optical properties make it a more technologically applicable nanocrystals.