Study of Nanocrystalline ZnAl2O4 and ZnFe2O4 with SiO2 on Structural and Optical Properties Synthesized by Sol-Gel Method

Zinc aluminate (ZnAl2O4) and zinc ferrite (ZnFe2O4) nanocrystalline structures dispersed into SiO2 matrix were prepared by sol-gel method. Phase formation of ZnAl2O4 and ZnFe2O4 was confirmed by X-ray diffraction (XRD) analysis. The crystallite sizes was determine using Scherer’s equation from the broadening of dominant peak at (311) plane. It was found the crystallite size of both compound decreased due to the decrement compositions of Zn2+ ion and Al3+ / Fe3+ ions. The crystallite sizes for ZnAl2O4 and ZnFe2O4 was calculated to be around ~ 14.16 – 11.27 nm and ~ 11.27 – 4.72 nm, respectively. FTIR analysis was done to determine the formation of spinel structures. FTIR results analysis confirmed that the formation of spinel structure where it has been observed that the bands around 800 cm-1 was associated to the vibrations of aluminum-oxygen and metal-oxygen-aluminum bonds. This characteristic was identified to the formation of zinc aluminate spinel structure. The optical properties have been done to determine the energy bandgap of ZnAl2O4 and ZnFe2O4 samples. The Uv-Visible absorption spectra have been done within wavelength 300 – 800 nm and the graph was plotted into the Tauc plot. This new dielectric material was purposed to improve the value of dielectric permittivity with addition of SiO2 where it can be applied as microwave dielectric material without changing the original spinel structures.