Lanthanum cobaltite black pigments with perovskite structure

In this work La1−xCaxCoO3 (x = 0–0.4) pigments were synthesized by the polymeric precursor method with heat treatments at 700, 800 and 900 °C for 4 h. The powders were characterized by colorimetry, UV–vis spectroscopy and powder X-ray diffraction (XRD). The X-ray diffraction patterns showed the presence of a single phase perovskite, changing its structure from rhombohedral to cubic, when calcium was added to the lattice. All of the pigments had a black colour with a strong absorption over the whole of the visible spectrum as a consequence of the different oxidation states of cobalt and the high short-range disorder. The substitution of Ca2+ for La3+ did not influence the pigment colour but decreased its final cost.