Preparation and Application of Apatite-TiO 2 Composite Opacifier: Preventing Titanium Glaze Yellowing through Pre-Combination.

In order to enhance the degree of binding reaction of TiO 2 in titanium-containing ceramic glazes and prevent the reaction of its transformation into rutile to eliminate the yellowing phenomenon of the glaze surface, an apatite-TiO 2 composite opacifier (ATO) was prepared through the mechanical grinding of hydroxyapatite and anatase TiO 2 . The properties, opacification mechanism, and yellowing inhibition of the prepared ceramic glazes were studied. The results show that the ATO is characterized by a uniform coating of TiO 2 on the surface of the apatite and the formation of close chemical bonding between the apatite and TiO 2 . The ceramic glaze surface when using an ATO has a white appearance and excellent opacification performance. When an ATO was used, the L*, a*, and b* values of the glaze were 89.99, -0.85, and 3.37, respectively, which were comparable to those of a ZrSiO 4 glaze (L*, a*, and b * were 88.24, -0.02, and 2.29, respectively). The opacification of the glaze was slightly lower than that of the TiO 2 glaze (L* value was 92.13), but the appearance changed from yellow to the white of the TiO 2 glaze (b* value was 9.18). The ceramic glaze layer when using an ATO mainly consists of titanite, glass phase, and a small amount of quartz, and the opacification mechanism is the crystallization of the generated titanite. ATOs can play an active role in solving the critical problem that arises when TiO 2 replaces ZrSiO 4 as an opacifier.