¹ The General Directorate for Education in Diyala, Baqubah 32001, Diyala, Iraq;

² Department of Physics, College of Science, Mustansiriyah University, Baghdad 10071, Iraq;

³ College of Education for Pure Science, Ibn Al Haitham, University of Baghdad, Baghdad 10071, Iraq

* Correspondence: taghreed.m.m@ihcoedu.uobaghdad.edu.iq

Zinc ferrite with composition (Zn_1-xCo_xFe₂O₄) (x = 0, 0.3, 0.4, 0.5, and 0.6) has been prepared using the sol-gel technique. The samples prepared were characterized using X-ray diffractometry (XRD) and transmission electron microscopy (TEM) techniques. The nanocrystallites have been found to have a size range of 63.023–99.036 nm. The optical properties for all samples' absorbance and energy band gap (Eg) were measured by the design of Tauc’s diagram. The indirect and (direct) optical band gaps of the synthesized (Zn_1-xCo_xFe₂O₄) ferrite increased from 2.65 eV to 3.40 eV and 4.07 eV to 4.60 eV with increasing the doping percentage of Co as x = 0–0.6. The increase in energy gaps (Eg) value with Co ions doping is possible because of sub-bandgap energy level formation.