Effects of doping iron on the colouring properties of copper chromate pigment

Abstract

Iron-doped copper chromate with (FexCu1–xCr2O4) as a black ceramic decoration pigment is successfully synthesized using a solid-state synthesis method with a pure oxide precursor. The powdered pigment was analysed using X-ray diffraction (PXRD), scanning electron microscopy (SEM), Fourier transform infrared analysis, ultra violet–visible and colour-measuring instruments. The calcination temperature was determined from literature at 1350 C for 3 h. The result of the PXRD indicated that the sample contains a spinel structure; moreover, the doping of iron caused the diffractogram peak to shift towards the lower angle due to the small ionic radius of iron compared to the replaced copper. The micrograph of the SEM indicated that the powder particles are well dispersed, and the energy dispersive spectroscopy result confirmed that all samples appear in their purest form. In addition, as the doped iron increases the colour axis of the pigment, L* tends to be more blackish, while the b* value turns more towards blue. However, the intensity of the red colour a* increases till half of the total copper is replaced by the doped iron and the optimal result was achieved which is comparable with commercial black pigment at Fe0.5Cu0.5Cr2O4, having L* = 32.96.