Effect of CaF2-, TiO2- and P2O5- on crystallization and properties of CaO–Al2O3–SiO2–ZrO2-based glass-ceramic glaze

The effects of three additives, CaF2, TiO2 and P2O5, on the crystallization, microstructure and properties of glass-ceramic glazes in the CaO–Al2O3–SiO2–ZrO2 system were investigated in detail. The results showed that CaF2 reduced the viscosity of the glaze and promoted the crystallization of t-ZrO2, as well as its conversion to ZrSiO4. The addition of TiO2 and P2O5 produced a phase-separated structure that favored t-ZrO2 crystallization but inhibited its transformation into ZrSiO4. The stronger the phase separation, the more pronounced this inhibition was. In glass-ceramic glaze containing P2O5 (named PG), t-ZrO2 was present even at 1250 °C, about 100 °C higher than in conventional zirconium glazes. Further TEM-EDS mapping analysis revealed that Zr was preferentially dissolved in the P-rich droplets. The lack of SiO2 and the diffusion barrier at the phase-separated interface were the main reasons for suppressing the transition from ZrO2 to ZrSiO4. After firing at 1200 °C, PG had a coexistence of ZrO2 and ZrSiO4 and exhibited optimal performance, with an L* value of 93.31, a whiteness of 86.5, a gloss of 91.9°, a hardness of 7.06 GPa and a roughness of 30.2 nm. These findings are valuable for the controlled crystallization of Zr-based glass ceramics and related products.