A combined experimental and theoretical optimization of the refractive index of NixMg1-xO solid solution for transparent nanocomposite applications

Abstract

The main objective of this work is to optimize the refractive index of MgO/NiO solid solution to increase the transparency of Y2O3–MgO (Y: M) nanocomposite in the visible region. First, various effective medium approximation theories (EMA) are applied to calculate the refractive index of NixMg1-xO solid solution as a function of NiO fraction and then determine those fractions giving the lowest refractive index mismatch with Y2O3 in the visible region. Thereafter, the theoretically predicted optimized solid solutions were experimentally synthesized by the sol-gel combustion method and the effect of NiO fraction on the morphology, structural properties, and band gap of the samples were investigated by the field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD), Fourier transform infrared (FTIR), and diffuse reflectance spectroscopy (DRS). We argued that increasing the NiO fraction will decrease the band gap of NixMg1-xO samples from 5.83 to 5.67 eV. Finally, we applied four phenomenological models to predict the static refractive index of the samples from their measured band gaps and concluded that NiO fraction of 28.5% likely minimizes the light scattering and consequently maximizes the transparency of the Ni0.285Mg0.715O–Y2O3 nanocomposite in the visible region.