Controlling the structural, linear and nonlinear optical and photoluminescent characteristics of NiCo<inf>2</inf>O<inf>4</inf> via alloying with MnS

Abstract

(1 − x)NiCo2O4/xMnS samples were formed using the hydrothermal and thermolysis process. Using X-ray diffraction data, phase identification disclosed a single phase solid solution (Ni/Mn)[Co/Mn]2(O/S)4 for all prepared samples, a solid solution from both cations and anions which is confirmed from analyzing Fourier-transform infrared spectroscopy measurements. The effect of incorporation of Mn on the cation distribution, lattice parameter, and crystallite size of NiCo2O4 (NCO) was studied using Rietveld analysis. X-ray photoelectron spectroscopy analysis manifested that NiCo2O4/MnS solid solutions contain abundant metal valence Mn2+, Mn3+, Co2+, Co3+, Ni2+ and Ni3+ which offer rich redox electron pairs, upgrading the NCO for many applications. Transmission electron microscope images revealed particles of nanosize (11 nm) with homogeneous morphology and very narrow size distribution. The influence of Mn and S ions insertion on the absorbance, extinction coefficient, refractive index, electric performance, and nonlinear parameters of NCO was explored using UV diffused absorption technique. Pristine NCO sample has two direct optical band gaps at 1.34 and 2.34 eV. Upon doping NCO with 10, 15 and 20% Mn and S ions, the optical band gaps changed to (1.32, 2.36), (1.28, 2.4) and (1.37, 2.19) eV, respectively. The photoluminescence intensity exhibited a maximum value as NCO doped with 10% Mn and S ions while it revealed a minimum value as the doping amount became 20%. The emitted colors depended on the amount of Mn and S introduced in NCO matrix.