Insight into the crystalline structure, morphology, luminescence, and electrical conductivity of ZnAl₂O₄:xMn²⁺ (0 ≤ x ≤ 2.0 mol%) nanostructures

Abstract

The ZnAl2O4: xMn2+ (0 ≤ x ≤ 2.0 mol %) spinel nanostructures were prepared by citrate sol-gel technique. X-ray diffraction (XRD) was used to acquire pure spinel structure while the nano crystallinity was assessed by transmission electron microscopy (TEM) of annealed powder samples. The prominent shift in diffraction angle has been noticed in doped samples. The nanocrystalline size was calculated in the range of 25-30 nm and Williamson Hall diagram was used to assess the micro stresses present in the samples. FTIR revealed the corresponding functional groups and emphasized the characteristic compositional bonds of normal spine structure. The data of UV-Visible spectroscopy manifests that ultraviolet absorption and bandgap energies attain remarkably lower values in the doped samples. The green luminescence is obtained at 519 nm via direct excitation of Mn2+ energy level which is controlled by the concentration of dopant as well as nanocrystallite size. The electrical characterization inferred the enhanced conductivity of the doped sample in which Mn2+ ions act as donor of electrons. The modified physical and optical properties of ZnAl2O4 after doping strengthen the useability of prepared metal aluminates in the optoelectronic devices of the semiconductor industry.