Abstract
The paper presents the results of investigation on the development of frits for single fast-firing glazes with variable BaO content based on the SiO2–Al2O3–CaO–MgO–ZnO–(BaO) system, fired at a maximum temperature of 1220 °C. The study of the correlation between the composition, structure and crystallization of frits and glazes was carried out using various methods for materials characterization, including differential scanning calorimetry (DSC), dilatometry (DIL), hot-stage microscopy (HSM), X-ray diffraction and scanning and transmission electron microscopy. DSC and X-ray diffraction showed a high tendency to crystallize the tested frits. DSC curves showed that all glazes crystallized during heating in a narrow-temperature range ≈ 938–955 °C, and the introduction of BaO shifted the maximum of exothermic peaks toward higher temperatures. X-ray analysis revealed the presence of diopside and anorthite as the main crystalline phases. The introduction of 5 mass% BaO to the frit composition promoted the crystallization of the additional crystalline phase of barium feldspar (BaAl2Si2O8). In addition, in this composition a strong exothermic effect on the DSC curve at the cooling stage was observed. The analysis of data obtained from thermal studies also showed that the addition of BaO to the chemical composition of the frits resulted in a decrease in the glass transition temperature (Tg) and in reduction in viscosity calculated on the basis of the Vogel–Fulcher–Tammann equation (HSM, DIL).
Highlights
It is known that glazes used in ceramic products play a decorative role and numerous protective functions, including protecting the material against soaking and harmful effects of chemicals [1,2,3]
The transformation temperature Tg determined from the thermal curves differential scanning calorimetry (DSC) related to the viscosity of the glass [32] slightly decreases for frits, for which up to 2.5 mass% of BaO (G 1.0Ba and G 2.5Ba) was introduced in relation to the G0 frit
The study investigated the correlation of the composition and influence of BaO addition on the structure and process of crystallization of fast-firing glazes from the MgO–CaO–Al2O3–SiO2–ZnO–(BaO) system
Summary
It is known that glazes used in ceramic products play a decorative role and numerous protective functions, including protecting the material against soaking (staining) and harmful effects of chemicals [1,2,3]. For example, for the production of sanitary products [3,4,5] or porcelain, and they are composed of Glazes with a high gloss level are useful in the production of wall tiles, due to the fact that they are usually characterized by lower abrasion resistance and lower microhardness [8]. Matt or semi-matte glazes are mostly used for floor tiles, and matt glazes are usually glass-crystalline materials characterized by increased resistance to abrasion. Depending on the frits used, it is possible to obtain smooth surfaces with a high gloss level [9] or even matt, glass-crystalline ones [8]. There are a number of works on various glass systems such as CaO–MgO–SiO2 [10, 11], CaO–MgO–Al2O3–SiO2 [11,12,13,14,15], Li2O–CaO–MgO–Al2O3–SiO2 [11, 16], (Na2O, K2O, ZrO2, ZnO)–CaO–MgO–Al2O3–SiO2 [14, 15, 17,18,19,20,21,22],
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