Structural and Optical Characterization of Ni and Al Co-Doped ZnO Nanopowders Synthesized via the Sol-Gel Process

Abstract

We have successfully synthesized (Ni,Al) co-doped ZnO nanostructured powders via the sol-gel technique at low temperature. The elemental analysis confirms the incorporation of the Ni and Al ions into the ZnO matrix. The structural study revealed that the nanopowder samples are assembled in flower-shaped Zn 0.9-x Ni 0.1 Al x O nanostructures with average crystallite sizes ranging from 39 to 53 nm. The XRD patterns show that the Zn 0.9-x Ni 0.1 Al x O nanopowders have a hexagonal wurtzite polycrystalline structure. Weak diffraction peaks related mainly to nickel oxides are also detected in the samples. The highest crystallite size, lowest lattice parameters and unit cell volume are obtained for the nanopowder samples that contain 1.5 at.% of aluminum. The decomposition process of the dried gel system is investigated by thermogravimetric analysis (TGA). Raman scattering and FT-IR measurements confirm the wurtzite structure of the synthesized Zn 0.9-x Ni 0.1 Al x O nanopowders. The energy band gap of the synthesized nanopowders (~3.32 eV) was estimated by using the Brus equation and the crystallite sizes obtained from XRD data, for comparison. The strain in the nanopowder samples (~2.7 × 10 -3 ) was also calculated according to the Stokes-Wilson equation.

Synthesis and Characterization of Nanocrystalline ZnO Doped with Al3+ and Ni2+ by a Sol–Gel Method Coupled with Ultrasound Irradiation

“…The broadening of band E 1 may occur due to oxygen vacancies originated by the incorporation of Al 3+ and Ni 2+ ions into the hexagonal lattice. This result agrees with those reported by Luthra and Sayari [28,31]. Raman spectra were recorded (Figure 2) under the same conditions for every sample.…”

“…In the ZnO-Ni sample, the absorption band gap was shifted to higher wavelengths due to interband transitions from the valence band A2g to the T2g level of Ni 2+ (3d 8 , 3A2g, 3T2g) by Ni 2+ . However, Al 3+ increases free electrons by replacing Zn 2+ in the ZnO network structure, hence generating conductivity in the semiconductor [31]. Figure 3 shows optical transmittance spectra of undoped and doped ZnO in the range 300-600 nm.…”

“…In the ZnO-Ni sample, the absorption band gap was shifted to higher wavelengths due to interband transitions from the valence band A 2g to the T 2g level of Ni 2+ (3d 8 , 3A 2g , 3T 2g ) by Ni 2+ . However, Al 3+ increases free electrons by replacing Zn 2+ in the ZnO network structure, hence generating conductivity in the semiconductor [31]. In Figure 4, photoluminescence spectra of the undoped and doped ZnO samples show a broad and intense emission spreading from 425 to 650 nm with an emission at 590 nm, while doped ZnO samples show that a shift at the 509 nm band is attributed to the presence of metal ions introduced by crystal defects such as oxygen vacancies because there are changes in the electronic band structure.…”

Annealing and Ni content effects on EPR and structural properties of Zn1–xNixO aerogel nanoparticles

“…Most of the ZnO crystals have been synthesized by traditional high-temperature solid-state method in which it is difficult to control the particle properties. However, ZnO nanoparticles can be prepared at low cost on a large scale by simple solution-based methods such as chemical precipitation, sol-gel process, and hydrothermal reaction [20][21][22][23][24].…”

Influence of aluminium concentration in Zn0:9V0:1O nanoparticles on structural and optical properties

“…Particularly, ZnO is a wide band gap semiconductor (3.3 eV) with a high exciton binding energy (60 meV) at room temperature, which has received more and more attention in the material science due to its various expected applications. ZnO nanomatererials have been realized by various techniques including thermal * E-mail: amor.sayari@laposte.net evaporation [1], chemical vapor deposition [2], sputtering [3], spray pyrolysis [4], pulsed laser deposition [5] and sol gel processes [6][7][8]. Among these methods, the sol gel process is particularly attractive because of its simplicity and acceptable costs for the large scale fabrication of nanostructure ZnO.…”