Ceramics-Silikáty 34, (3) 229 - 239 (1990)

Fluorides and chlorides, particularly the combinations BaF₂ + CaF₂ or LiF + NaCl, appear to be the most efficient mineralizing additions for the preparation of grey zircon pigments of the ZrSi-AlNiCo or ZrSi NiCoCrFe types with respect to their optical properties. At a mean 30 % spectral reflectance, the difference between the highest and the lowest value amounts to 5 % . A black pigment of the rutile type (TiSbV) was prepared under various conditions of reaction mixture composition and firing. In view of the optical properties (optimum flatness of the spectral reflectance curve) and of the amount of eluable vanadium, the following composition and firing conditions were found to be the most suitable ones: the Sb : V molar ratio = 1.4 : 0.6, 20 wt.% admixtures in the form of Sb₂O₃ and NH₄VO₃ , firing at 1150 to 1200 °C for 2 hours. The pigment is made from TiO₂ of Czechoslovak manufacture, Pretiox AV 01, has a flat spectral reflectance curve and a vanadium eluability of 0.02 % of the calcinate weight.