Novel terbium-zircon yellow pigment

Abstract

The incorporation of the terbium oxide into the zircon host lattice in the presence of different types (NaF and LiF) and amounts (2 and 5 wt%) of mineralisers created various shades of yellow at several calcination temperatures with 2 h soaking time. The shade of yellow observed was primarily a lemon yellow, different from existing Pr-Zircon yellow. The pigment powders were characterised using techniques such as XRD, SEM, Particle Size Analysis and Spectrophotometry. From the X-ray diffraction patterns, zircon was found to be the major phase present together with small amounts of un-reacted zirconia. The amount of un-reacted zirconia in each case was calculated using an external standard method. SEM micrographs of the samples indicated growth of the tetrahedral shaped crystals improved on addition of sodium fluoride. The same zircon crystals were observed to form with the use of lithium fluoride as a mineraliser, but the shape of the crystals differed. The average particle size was found to vary between 11–15 μm. Stability of these pigment powders was tested in an unleaded commercial transparent glaze. Yellow coloured glazed tiles were produced suggesting that the pigments were stable in the commercial unleaded transparent glaze. Colour measurements were performed on the pigment powder samples and on the coloured glazed tiles.