Synthesis and Characterization of Er-Doped Nano ZnO Samples

Abstract

Pure and erbium-doped ZnO nanoparticles (Zn1−xErxO), (0.00 ≤ x ≤ 0.10), were synthesized by wet chemical co-precipitation method. The structural, optical, and magnetic properties of the prepared samples were investigated using x-ray powder diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV), Fourier transform infrared spectroscopy (FTIR), M-H magnetic hysteresis, and electron paramagnetic resonance (EPR). XRD studies exhibit the presence of a single ZnO wurtzite hexagonal crystal structure for 0.00 ≤ x ≤ 0.06. A secondary phase of Er2O3 appears for x > 0.06. This means that the solubility limit for doping Zn2+ ions by Er3+ ions is about x = 0.06 under our preparations condition. The lattice parameter a is not affected by the Erbium doping. On the other hand, the lattice parameter c and the unit cell volume V increase with the increase of x up to x = 0.06. This is attributed to the larger ionic size of Er3+ ions (0.88 A) compared to Zn2+ ions (0.74 A). Both c and V decrease for x > 0.06. TEM micrographs indicate that the shape and the size of the ZnO nanoparticles are modified by changing the doping level of Er. The UV measurements point out that band gap energy Eg decreases with the increase of x up to x = 0.06. Then, it increases for both x = 0.08 and 0.10. FTIR spectra confirm the presence of O–H and Zn–O stretching modes at 3451.963 and 428.901 cm− 1, respectively, in pure and doped ZnO samples. The Zn–O stretching mode shifts toward a lower wavenumber for x = 0.06 and toward a higher wavenumber for x = 0.10. M-H hysteresis analysis, at room temperature, reveals that the pure ZnO has a ferromagnetic signal combined with diamagnetic and paramagnetic contributions. This ferromagnetism is reduced for the doped samples up to x = 0.02, and an antiferromagnetic alignment appears for 0.04 ≤ x ≤ 0.10. The saturation magnetization (Ms), the coercivity (Hc), the retentivity (Mr), the anisotropy constant (Ka), and the magnetic moment (μm) were estimated and discussed in terms of erbium doping for the different samples. EPR spectra for Zn1−xErxO were measured at room temperature in order to study the effect of Er substitution on the g value, resonance field (Hr), peak to peak line width (ΔHpp) and spin–spin relaxation time constant (T2).