Correlation between degree of crystallinity and bluing of Zn1–xCoxAl2O4 (0≤x≤1) nanopowders prepared by soft chemistry route

Abstract

In this article, we report a facile precursor pyrolysis by sol-gel method to prepare spinel-type Cobalt-substituted zinc aluminate nanoparticles (Zn1–xCoxAl2O4, 0 ≤ x ≤ 1). The relationship between the degree of crystallinity and the optical properties under the effect of the calcination temperature was investigated. The synthesised powders were characterized by means of X-ray diffraction (XRD), Thermogravimetry and Differential thermal analysis (TG–DTA), field emission scanning electron microscopy (FE-SEM), Brunauer–Emmett–Teller analysis (BET), UV–Vis absorption spectroscopy analysis and colorimetric analysis (CIELab). A single-phase Zn1–xCoxAl2O4 (0 ≤ x ≤ 1) spinel was formed at an annealing temperature of 700 °C. Structural refinement via the Rietveld method shows that an annealing temperature in excess of 700 °C leads to a decrease in the amorphous phase rate. At 800 °C, the enrichment in 50% of cobalt leads to blue powders with a degree of crystallinity of approximately 92% and a quasi-spherical morphology of nanometric size less than 100 nm.