Development of novel low-BaO based glass-ceramic glazes for porcelain stoneware tiles

In this study, novel glass-ceramic glazes are formulated for porcelain stoneware tiles to assess the impact of BaO concentration on their surface and aesthetic characteristics. The investigated glazes are within the Na 2 O-K 2 O-CaO-MgO-BaO-ZnO-Al 2 O 3 -SiO 2 system, with BaO content from 1.1 to 3.5 mol%. Unlike previous studies, this work provides a comprehensive assessment including Vickers microhardness, scratch resistance, and surface roughness, in addition to microstructural and thermal characterization. The results show that between 2.5 and 3.5 mol% BaO, glaze microstructure exhibits the coexistence of Na-anorthite and hyalophane crystals, while for 1.1 mol% BaO, (Ba, Na)-orthoclase and Na-anorthite are observed. Variations in crystalline phases, as well as in the amount of amorphous phase, significantly influence the final surface properties. The best performance in terms of Vickers microhardness, scratch resistance, surface roughness, and gloss is achieved for 2.5 mol% BaO and a crystalline content of 64%.