Influence of K2O/(CaO+ZnO) ratio on crystallization behavior, phase formation, and properties of transparent borosilicate glazes

Razie Salami; Aida Faeghinia; Zahra Khakpour; Mohammad Zakeri

doi:10.53063/synsint.2026.62331

Razie Salami ¹
Aida Faeghinia ¹
Zahra Khakpour ¹
Mohammad Zakeri ¹

¹ Ceramics Department, Materials and Energy Research Center (MERC), Karaj, Iran

https://doi.org/10.53063/synsint.2026.62331

Abstract

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.

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Keywords: Transparent borosilicate glaze, Glass–ceramics, Crystallization, Phase evolution, Properties

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