Electronic structure and optical properties of spinel structure Zn1-xNixAl2O4 nanopowders synthesized by sol-gel method

Zn1-xNixAl2O4 (x = 0, 0.025, 0.05, 0.075, and 0.10) nanoparticles with spinel structure were synthesized by sol-gel technique and the band structure of various defects in the ZnAl2O4 structure was calculated using the first-principles method. The average grain size and lattice parameters vary with doping concentration. Ni ions are successfully substituted for the lattice site of Zn2+ into the ZnAl2O4 matrix, Ni ions mainly occupy the tetrahedral sites, and the substitution of Ni introduced new energy levels. The photoluminescence spectral intensity of doped samples decreases, resulting in luminescence quenching. The bandgap decreases with the increase of Ni ion concentration, presenting a redshift.