In this study, we investigated the effects of dimorphous nucleating agents-rutile TiO₂ and anatase TiO₂, on the crystallization and surface properties of ZnO-Al₂O₃-CaO-SiO₂-based glass. Glass specimens were prepared by substituting rutile TiO₂ and anatase TiO₂ at 1, 3, and 5 wt.% and subsequently heat treating at 1050 °C for 90 min to induce crystallization. The crystallization characteristics and surface properties of the crystallized glass were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), gloss, Fourier-transform infrared (FTIR) spectroscopy, hardness, and colorimetric analyses. The XRD and SEM analyses revealed the presence of a titanite crystalline phase in the glass matrix. However, the addition of anatase TiO₂ as a nucleating agent resulted in a significant decrease in glossiness. FTIR deconvolution in the range of 800-1300 cm⁻¹ showed an increase in the degree of [SiO₄] tetrahedral polymerization with higher levels of crystallization. micro-Vickers hardness of the glass specimens increased from the original value of 6.32 GPa to a maximum of 7.05 GPa, indicating enhanced hardness due to crystallization. Colorimetric analysis indicated that the inclusion of rutile TiO₂ as a nucleating agent increased the Yellow Index of anatase TiO₂

Keywords: Glass-ceramics, Crystallization, Rutile/Anatase TiO₂, Surface properties