The Effect of Ni2+ Ions Substitution on Structural, Morphological, and Optical Properties in CoCr2O4 Matrix as Pigments in Ceramic Glazes.

The structural, morphological, and optical properties of Ni2+ ions substitution in CoCr2O4 matrix as ceramic pigments were investigated. The thermal decomposition of the dried gel was performed aiming to understand the mass changes during annealing. The X-ray diffraction (XRD) studies reveal a spinel-type Face-Centered Cubic structure and a secondary Cr2O3 phase when x ≤ 0.75 and a Body-Centered Tetragonal structure when x = 1. Fourier Transform Infrared Spectroscopy (FT-IR) indicated two strong absorption bands corresponding to the metal-oxygen stretching from tetrahedral and octahedral sites, characteristic of spinel structure. Ultraviolet-Visible (UV-Vis) spectra exhibited the electronic transitions of the Cr2+ Cr3+ and Ni2+ ions. From the UV-Vis data, the CIE color coordinates, (x, y) of the pigments were evaluated. The morphology was examined by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) showing the agglomeration behavior of the particles. The stability, coloring properties and potential ceramic applications of studied pigments were tested by their incorporation in matte and glossy tile glazes followed by the application of obtained glazes on ceramic tiles. This study highlights the change in pigment color (from turquoise to a yellowish green) with Ni2+ ions substitution in the CoCr2O4 spinel matrix.