Synthesis of yttrium aluminate doped with Cr3+ using MgF2–Na2B4O7 as mineralizers to obtain red pigments for ceramic tiles application

Abstract

Ceramic pigments based on chromium-doped yttrium aluminate (YAl1-XCrXO3; x = 0.01; 0.03 and 0.05 mol%) were obtained by using chemical combustion method. Chemical processes with and without the use of mineralizers were employed. The modifications in the structure, morphology, optical and thermal properties caused by the inserted agents in the aluminate network were investigated by means of the following techniques: X-ray diffraction (XRD), Rietveld refinement, diffuse reflectance spectroscopy in the ultraviolet–visible region (UV–Vis), Fourier-transform infrared (FTIR) spectroscopy, field emission gun scanning electron microscopy (FEG-SEM), and CIELab colorimetric coordinates. The pigments were applied to ceramic pieces and the color stability was evaluated. XRD patterns results coupled with Rietveld refinement analyses showed a pronounced phase evolution for the samples containing mineralizers. This confirmed the effectiveness of these constituents for the formation of yttrium aluminate perovskite phase. The UV–Vis spectra showed greater reflectance in samples without mineralizers, while FTIR spectroscopy Analysis showed bands of vibration related to Al3+ coordinated octahedrally for both systems. Samples with the presence of mineralizer agents showed morphology similar to a cube with the presence of primary aggregated particles as revealed by FEG-SEM. The colorimetric pigments data showed values of the a* coordinate, which is related to red color components. This value was higher for the powder in the system with mineralizers as well as in the pigments that were employed on the ceramic pieces.