Structural, optical and magnetic properties of Co-doped ZnO nanoparticles prepared via a wet chemical route

Abstract

In this paper, ZnO nanoparticles doped with varying amount of Co content (i.e., 0, 2, 4, 6, 8, and 10 at.%) have been prepared by wet chemical route. X-ray diffraction (XRD) results reveal the successful substitution of Co 2+ ions on to sites of Zn 2+ ions without forming any secondary phase. Furthermore, a linear increase in d-spacing of the ZnO lattice is found with the increase in Co content. SEM images demonstrate the formation of homogeneously distributed spherical nanoparticles with average size of 50–70 nm. It is observed from optical investigations that band gap energy of ZnO nanoparticles significantly decreased with the increase in Co doping level. Interestingly, it is found that the high Co dopant concentration can lead to room temperature ferromagnetism in ZnO nanoparticles.

Structural, optical, thermoelectrical, and magnetic study of Zn1‐xCoxO (0 ≤ x ≤ 0.10) nanocrystals

“…In fact, the Co 2+ ions first easily enter into the ZnO sites by increasing the level of impurity to 6%, and then, substitute into the ZnO matrix, which leads to an increase in the interplanar spacing d of (002) and (101). The linear increase in the interplanar spacing d of (002) from x = 0% to x = 6% is in agreement with the studies of previous researchers . The change in the lattice parameters a and c vs doped Co, as shown in Figure C, reveals significant an increase the level of Co impurity x = 0.02, which is in agreement with previous research .…”

“…Owing to the direct band transition in ZnO, the direct optical band gap energy of each sample is calculated from their reflectance spectra by the extrapolation of the linear region of (F(R)h υ ) 2 plot vs E(h υ ) to the energy axis when (F(R)h υ ) 2 = 0 , where R is percentage reflection and F(R) is the Kubelka‐Munk function, which is shown in Figure . It is interesting to note that when the Co concentration is increased for the Co x Zn 1‐x O nanocomposite (x = 0, 0.02, 0.04, 0.06, and 0.10), the band gap energy is decreased to 3.15, 2.88, 2.75, 2.73, and 2.36 eV, respectively, which is in agreement with the previous investigations for the impurity of 2%, and it is improved for the impurities (>2%) compared to the other studies . This means that the value of the band gap decreases with Co impurity, which is evidenced by a red‐shift in the band gap energy .…”

“…The linear increase in the interplanar spacing d of (002) from x = 0% to x = 6% is in agreement with the studies of previous researchers. 45,46 The change in the lattice parameters a and c vs doped Co, as shown in Figure 2C, reveals significant an increase the level of Co impurity x = 0.02, which is in agreement with previous research. 45 This indicates that Co ions reside in the ZnO lattice, whereas there is not an obvious change in lattice parameter values for x = 0.04 and 0.06 of Co impurities.…”

“…42,43 A special shift in the position of the peaks toward lower 2h values with Co concentration, suggesting that all of the Co 2+ ions are not completely substituted in the ZnO matrix because there is a difference of about 0.002 nm between the Co and the Zn ionic radius, which is in accordance with the previous studies. [44][45][46] In fact, the Co 2+ ions first easily enter into the ZnO sites by increasing the level of impurity to 6%, and then, substitute into the ZnO matrix, which leads to an increase in the interplanar spacing d of (002) and (101). The linear increase in the interplanar spacing d of (002) from x = 0% to x = 6% is in agreement with the studies of previous researchers.…”

Effect of Co Doping on Structural and Optical Properties of Zinc Oxide Nanoparticles Synthesized by Sol-Gel Method

“…The advantages of using sol-gel processing instead of high temperature processing methods are: low synthesis temperature, high purity, novel materials, and low capital costs [14]. The effect of cobalt incorporation on structural and optical properties was investigated using X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques [15].…”