Effect of 10% Ag doping on the structural, optical, and electrical properties of ZnAl₂O₄ nanoparticles for optoelectronic studies

This work investigates the structural, optical, dielectric, and electrical properties of nominally 10% Ag-doped 𝑍 𝑛 𝐴 𝑙 ⁢ ₂ ⁢ 𝑂 ⁢ ₄ spinel nanoparticles synthesized by the sol–gel auto-combustion method. X-ray diffraction combined with Rietveld refinement confirms a cubic 𝑍 𝑛 𝐴 𝑙 ⁢ ₂ ⁢ 𝑂 ⁢ ₄ spinel main phase accompanied by a minor metallic Ag phase, while SEM, TEM, and EDX analyses reveal slightly agglomerated quasi-spherical nanoparticles with a relatively homogeneous elemental distribution. The material exhibits a direct optical band gap of 3.810 eV, an Urbach energy of 0.767 eV, and a refractive index of about 3.00. Linear and nonlinear optical parameters were evaluated from experimental optical constants using semi-empirical models; the nonlinear susceptibilities were estimated through Miller’s rule rather than measured directly. Dielectric and electrical measurements show pronounced frequency- and temperature-dependent behavior, with thermally activated charge transport and activation energies ranging from 0.303 to 0.483 eV. The frequency dependence of the conductivity is consistent with correlated barrier hopping, while the small-polaron hopping analysis provides complementary activation-energy estimates. These results demonstrate that Ag incorporation modifies the optical and electrical response of the 𝑍 𝑛 𝐴 𝑙 ⁢ ₂ ⁢ 𝑂 ⁢ ₄ matrix and may be relevant to future optoelectronic and electronic studies, although dedicated device measurements are required to establish application performance.