One-Pot Microwave Combustion Synthesis of Porous Zn_1–x Cu _x Al₂O₄ (0 ≤ x ≤ 0.5) Spinel Nanostructures

Porous Zn_1–x Cu _x Al₂O₄ (x =0,0.1,0.2,0.3,0.4,0.5) spinel nanostructures were synthesized by one-pot microwave combustion technique. All the samples were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and scanning electron microscopy (SEM). The XRD patterns confirm the formation of single phase ZnAl₂O₄ without any impurities. The results of XRD indicated the average crystallite size in the range of 12.44–22.86 nm. FT-IR spectra show the vibrational stretching frequencies corresponding to the zinc aluminate spinel structure. The estimated band gap of undoped ZnAl₂O₄ was 4.96 eV indicating the quantum confinement phenomenon. DRS spectra also indicated the band gap narrowing effect with increase in copper ion concentrations. The defect centers acting as trap levels were obtained from photoluminescence studies responsible for the emission spectra. SEM images showed the features of well created pore structures in all the matrices. The percentage porosity of zinc aluminate matrices decreased with increasing copper doping.