<p>Zn_1−xNi_xAl₂O₄ (x = 0.0, 0.25, and 0.5) was synthesized via a solid-state reaction method. Structural parameters were refined using the Rietveld method, and the obtained cation distributions were confirmed by FTIR and Raman spectroscopy. Transmission electron microscopy (TEM) revealed homogeneous particle morphology consisting mainly of spheroidal shapes with occasional rectangular formations. Field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray spectroscopy (EDS) showed that the elemental compositions deviated only slightly from the nominal values. The optical band gap of pristine ZnAl₂O₄ was determined to be 3.24 eV, which decreased to 1.37 eV and 1.34 eV upon Ni doping at x = 0.25 and x = 0.50, respectively. The refractive index (n) of ZnAl₂O₄ increased with Ni incorporation, showing a marginal rise with higher Ni content. The dielectric constant, optical conductivity, and nonlinear optical parameters were enhanced with increasing Ni doping. The effect of Ni doping on the photoluminescence properties of ZnAl₂O₄ was also investigated. The pristine ZnAl₂O₄ exhibited diamagnetic behavior, whereas the Ni-doped samples showed paramagnetic characteristics.</p> Graphical Abstract <p></p>