Improvement of structural and optical properties of ZnAl₂O₄:Cr³⁺ ceramics with surface modification by using various concentrations of zinc acetate

The influence of surface modification with various concentrations of zinc acetate solution on the structural and optical properties of ZnAl₂O₄:Cr³⁺ particles was studied. The X-ray diffraction peaks assigned to the spinel structure of ZnAl₂O₄:Cr³⁺ powders revealed a tiny shift towards the lower angle, and ZnO phase was detected when ZnAl₂O₄:Cr³⁺ crystals surface was modified. The results of X-ray photoelectron spectra confirmed that the antisite defects related to tetrahedral Al existed in the surface lattices of zinc aluminate crystals. The signal intensity of XPS assigned to tetrahedral Al decreased after surface modification, while that of XPS assigned to octahedral Zn increased. The results of transmission electron microscope showed that the surface lattices of ZnAl₂O₄:Cr³⁺ particles became more ordered after surface modification, and zinc oxide nanocrystals were observed as a coating layer or dispersed particles surrounding ZnAl₂O₄:Cr³⁺ particles when the concentration of Zn(AC)₂ solution increased up to 1.5 mol/L. The red emission assigned to Cr³⁺ ions in spinel lattices was detected at room temperature, and the emission intensity was enhanced when ZnAl₂O₄:Cr³⁺ crystals was modified. While the emission intensity was reduced when the concentration of Zn(AC)₂ solution increased up to 1.5 mol/L.