Industrially available blue ceramic pigments, with the exception of vanadium–zircon blue, (Zr,V)SiO₄, contain Co. To minimise the use of toxic and scarce cobalt, while also maintaining an intense blue colour, the performance as blue ceramic pigments of both Co²⁺–Zn₂SiO₄ (willemite) and Zn²⁺–Co₂SiO₄ (olivine) solid solutions was studied. The addition of cobalt in the willemite lattice was minimised. A wide range of compositions, Co_xZn_2−xSiO₄ (x = 2, 1.95, 1.5, 1, 0.9, 0.5, 0.05 and 0), were prepared and characterised by X-ray diffraction, lattice parameter measurements, UV–VIS–NIR spectroscopy, CIE-L*a*b* colour measurements and electronic microscopy (SEM/EDAX). The results show that an intense and more blue ceramic pigment is obtained based on the willemite lattice, with an optimised, low Co content, ranging from 25 mol% Co (Co_0.5Zn_1.5SiO₄) to 2.5 mol% Co (Co_0.05Zn_1.95SiO₄). This last composition (with only 2.5 mol% Co) exhibits the best blue hue once enamelled (b* = −39), though it is also considerably lighter (L* = 57).

Ln–CeO₂ (Ln = Pr, Tb, Eu) and M–CeO₂ solid solutions (reference samples with M = Cr or In, as transition and main group elements, respectively) have been prepared by ceramic and coprecipitation routes. The resulting coloured materials have been checked as potential pigments for porcelainised stoneware. The colouring mechanism is based on the introduction of an additional electronic level of energy in cerianite forbidden band, arising from unpaired 4f electrons of lanthanide ions. The red ceramic pigments obtained have been found to be interesting alternatives for the coloration of porcelainised stoneware bodies. In addition, they present a much lower toxicity than classical cadmium sulfoselenide or chromium–LnAlO₃ based red pigments, because both the chromophoric agent (praseodymium and europium ions) and ceramic matrix (cerianite) contain lanthanide elements.