Evaluation of surface characteristics and natural radioactivity of mineral-based glaze according to zircon substitution

Zircon (ZrSiO4) is widely utilized as an opacifying agent in the glazes of sanitary-ware and ceramic tile. Zircon is dispersed in the glassy phase during the manufacture process of glaze, contributing a high refractive index and enhanced mechanical properties. However, significant price fluctuation and natural radioactivity of zircon have motivated extensive research to find alternative compositions. This study investigates the surface characteristics and radiation properties of sanitary-ware glazes prepared by replacing zircon with SnO2 and CaTiO3 in the raw materials. Analysis of the radioactivity index (Iγ) for glaze raw materials revealed that zircon exhibited the radioactivity index of 9.7, which is significantly higher than that of other mineral-based raw materials. To reduce the radiation emission from glaze, zircon was replaced with CaTiO3 and SnO2, which are radiation-free materials. The glaze prepared using CaTiO3 and SnO2 showed thermal behavior and surface characteristics comparable to those of zircon-containing glaze. Furthermore, the radioactivity index of clay specimen coated with zircon-containing glaze was measured at 1.09, while the radioactivity index of clay specimen coated with zircon-free glaze was significantly reduced to 0.62.