Influence of K2O/(CaO+ZnO) ratio on crystallization behavior, phase formation, and properties of transparent borosilicate glazes en en The crystallization behavior of transparent borosilicate glass–ceramic glazes is strongly influenced by the composition of network-modifying oxides, which governs phase evolution and the resulting functional properties. In this study, the effect of the K2O/(CaO+ZnO) ratio on the thermal behavior, structural evolution, phase formation, microstructure, optical properties, and mechanical performance of transparent borosilicate glazes was systematically investigated. Glass frits with different K2O/(CaO+ZnO) ratios were prepared using the conventional melt-quenching method, applied onto ceramic substrates, and fired under identical conditions. The resulting glazes were characterized by differential thermal analysis (DTA), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), optical measurements, and Vickers microhardness testing. The results showed that decreasing the K2O/(CaO+ZnO) ratio significantly increased the glass transition temperature, indicating improved thermal stability of the parent glass, while only slightly affecting the crystallization peak temperature. Structural modifications of the borosilicate network promoted systematic changes in the crystalline phase assemblage, leading to the formation of anorthite, willemite, and calcium silicate phases with distinct crystal morphologies. Increased crystallization at lower K2O/(CaO+ZnO) ratios reduced the gloss of the fired glazes because of enhanced light scattering, whereas the formation of harder crystalline phases improved the microhardness of the glass–ceramic coatings. These findings demonstrate that the K2O/(CaO+ZnO) ratio is an effective compositional parameter for controlling the structure–property relationships of transparent borosilicate glazes and provides a practical strategy for optimizing their crystallization behavior and overall performance. 155 162 Raziye Salami Ceramics Department, Materials and Energy Research Center (MERC), Karaj Iran Aida Faeghinia Ceramics Department, Materials and Energy Research Center (MERC), Karaj Iran a.faeghinia@merc.ac.ir Zahra Khakpour Ceramics Department, Materials and Energy Research Center (MERC), Karaj Iran Mohammad Zakeri Ceramics Department, Materials and Energy Research Center (MERC), Karaj Iran Transparent borosilicate glaze Glass–ceramics Crystallization Phase evolution Properties Vol 6 No 2 Paper 7.pdf [1] S. Wang, X. Li, C. Wang, M. Bai, X. Zhou, et al., Anorthite-based transparent glass-ceramic glaze for ceramic tiles: Preparation and crystallization mechanism, J. Eur. Ceram. 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