Preparation and characterisation of green nano-sized ceramic pigments with the spinel structure AB2O4 (A = Co, Ni and B = Cr, Al)

Abstract Inorganic pigments based on AB2O4 (A = Co, Ni; B = Cr, Al) spinel structures with green colour were successfully synthesised by the polymeric route. The effect of the substitution of trivalent and divalent cations on the structural, optical and morphological properties of the pigments was investigated. The synthesised nanopowders were examined using thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller analysis (BET), UV–vis diffuse reflectance measurements, and CIEL*a*b* colorimetric analyses. The results show that the CoCr2O4 spinel and the spinels substituted by nickel and aluminium cations were obtained with a single phase after heat treatment at 900 °C. The produced powders present shades of the green colour with improvement in morphology for the substituted samples. The Ni0·5Co0·5CrAlO4 nanoparticles consisted of grains of quasi-spherical shape with sizes between 50 and 75 nm. This powder was used in small quantities with glazes for colouring tests on the surfaces of ceramic substrates.