Cu- and Mn-doped forsterite: sol–gel synthesis, and optical and colorimetric investigation

Abstract

Cu-doped forsterite Mg2−xCuxSiO4 (0.1 ≤ x ≤ 0.6) and Mn-doped forsterite Mg2−xMnxSiO4 (0.2 ≤ x ≤ 1) powders have been prepared by sol–gel method and characterized by XRD, SEM–EDS mapping, UV–Vis–NIR spectroscopy and CIE L*a*b* colour measurements to be explored as powdered ceramic pigments. The use of a sol–gel method based on silicic acid (H2Si2O5)aq and mineralizers (KCl and NaCl) along with a thermal treatment at 1200°C for 3 h, led to the formation of highly pure materials. The presence of Cu and Mn ions in the M1 and M2 sites was the main origin of the pigments colour. The latter was mostly affected by the chromophore’s valence state and concentration, and some formed minor phases. Besides that, the pigments with low doping levels showed very nice and attractive blue (Cu) and purple (Mn), making them interesting less toxic and less expensive ceramic pigment candidates.