Structural, Optical & Magnetic Properties of (Fe, Al) Co-Doped Zinc Oxide Nanoparticles

Received : 14-01-2019 Accepted : 05-02-2019 Abstract: Pure and (Fe, Al) co-doped ZnO nanopowders are prepared via coprecipitation method constructively with PEG as capping agent at room temperature (RT). We kept the aluminum concentration as constant at 5 mol% by altering the iron concentration from one to three mol%. After the finishing point of synthesis, the powders are cautiously subjected to various characterizations for instance XRD, Raman, SEM through EDS, TEM, PL, UV-Vis-NIR and VSM, to analyze the properties of structural , morphological, optical and magnetic. XRD analysis reveals, all the nanopowder samples acquire hexagonal wurtzite structure by the nonexistence of secondary peaks involving to aluminum or iron. This reveals the well dissolving of aluminum and iron in to Zinc Oxide host lattice. The literal size of nanocrystallites is evaluated through TEM pictures, which are approximately corroborated by the XRD calculations. The nanostructures morphology is found through SEM illustrations, and the spectrum of EDS shows that no impurities are existence other than iron and aluminum. Optical properties are deliberated by the PL spectrum and UV-Vis-NIR spectrum; all the powder samples encompass defect associated peaks over the visible range. Magnetic properties are evaluated using VSM and all the co-doped samples contain the Ferromagnetic nature except pristine Zinc Oxide.


XRD Studies
The

Raman Analysis
Raman spectroscopy is the excellent method for determining the integration of dopant materials, and disorders in the ZnO [42]. Involving to doping elements, the surface is changed due to transport of charge connecting to host lattice and doping material, where it varies the optical Raman spectrum [43]. Raman spectra are recorded for pristine and co-doped ZnO nanoparticles in the ambit of 0 cm -1 to 1200 cm -1 and are given in the figure 2 and figure 3 respectively. Raman spectroscopy of pristine ZnO illustrate the peaks by 157 cm -1 , 329 cm -1 , 581cm -1 , which are ascribed to first and second order vibration modes of ZnO nanostructures [44]. The Raman intensive peak appeared at 437 cm -1 ascribed to higher frequency (E2H) mode, supplementary peaks appeared at 330 cm -1 and 831 cm -1 could belongs to multi phonon modes E2H-E2L and (A1(TO)+E2L) respectively. One more peak appeared at 881 cm -1 belongs to Zn-O-Zn vibration mode [45]. Figure 3 shows the Raman spectroscopy of (Fe, Al) co-doped ZnO nanoparticles and this spectrum reveals supplementary peaks besides the Raman modes identified in the pure ZnO nanoparticles. The Raman spectroscopy of all three samples of co-doped ZnO reveals the wide peak at 573 cm -1 which is A1LO symmetry mode [46][47][48]. Another peak appeared at 640 cm -1 is associated to intrinsic defects of host lattice ZnO after adding Fe into ZnO, also it is confirmation to prove the occupation of Fe at Zn sites in the host lattice [49][50][51].

SEM and EDS Studies
Scanning electron microscope is a tool to approximate the surface morphology of undoped and co-

TEM, HRTEM AND SAED Observations
Transmission electron microscopy is the best tool to approximate the exact size of the pristine and co-doped ZnO nanoparticles. Figure 6

Photoluminescence (PL) Spectrum Analysis
Photo luminescence spectroscopy (PL Spectrum) is

Photoluminescence (PL) Spectrum Analysis
The pure ZnO and co-doped ZnO nanopowders are characterized by UV-Vis-NIR Spectrometer in wavelength region of 200-800 nm. Figure 9 shows the Optical absorption spectra of pure and co-doped ZnO nanopowders. The spectrum reveals the absorption edge in the ambit of 376 nm, which is the characteristic feature of ZnO host lattice.

Magnetic Studies
Room temperature magnetization (M-H) curves of (Fe, Al) co-doped ZnO nanoparticles are given in the figure10.   Pure ZnO shows diamagnetic nature as we are not mentioned in the graph here, it is familiar that pristine bulk ZnO shows diamagnetic nature, however recent reports showed that pristine ZnO might show ferromagnetic nature under certain film thickness [56], others also reported Room Temperature Ferromagnetism (RTFM) in pure ZnO [57][58].