Influence of Cr doping on the structural, optical, and third-order nonlinear optical properties of ZnAl2O4 nanoceramics

In this research, Zn(1−x)CrxAl2O4 (x = 0.00, 0.05, 0.10, 0.20) nanoparticles were prepared by a simple and green chemistry synthesis using gelatin as a polymerization agent. X-ray diffraction technique and scanning electron microscopy imaging were used to analyze the structural and morphological properties of the samples. X-ray diffraction results revealed that all samples were polycrystalline and crystallized in a cubical spinel phase. With increasing the x from 0.00 to 0.20, the main Bragg peaks shift to smaller angles, and the crystallite size and energy bandgap of samples decrease as well. The nonlinear absorption coefficient, β, and nonlinear refractive index, n2, of Zn(1−x)CrxAl2O4 were meticulously studied by the Z-scan approach. The orders of n2 and β are 10−7 and 10−4 cm/W, respectively. The saturable absorption and the self-defocusing effect are the main factors in the appearance of β and n2, respectively. The experimental results confirmed that increasing the percentage of Cr caused nonlinear coefficients to increase.