Ceramic Pigments on Apatite Basis

A process for preparing a compound having the general formula M5(AO4)3X, wherein M represents Ba, Sr, Ca or a mixture thereof and A represents P, V or a mixture thereof, and wherein the group M5(AO4)3 forms an apatite structure and X is situated in the hexagonal channels of the apatite structure and includes Cu-atoms, with the proviso that the compound is not Sr5(VO4)3(CuO), Sr5(VO4)3(Cu0.894O0.952), or (Sr0.9Ca0.1)5(CrVO4)3(CuO), the process comprising the steps of:

• (i) mixing of compounds comprising the elements M, A and X;
• (ii) a first thermal treatment of the mixture in the range of 200 to 1700° C., wherein the thermal treatment is performed in ambient air;
• and
• (iii) a second thermal treatment of the mixture in the range of 500 to 900° C.

Pigment comprising a compound prepared by a process comprising the steps of:

• (i) mixing of carbonates of M, Cu-compounds, and (NH4)H2PO4 or a V-compound or mixtures thereof,
• (ii) thermal treatment of this mixture in solid state in air at 600 to 850° C. for 1 to 5 hours,
• (iii) regrinding,
• (iv) thermal treatment in air at 1100 to 1400° C. for about 1 to 24 hours,
• (v) air quenching and
• (vi) regrinding.