Impact of barium oxide on the structure and surface properties of glass-crystalline glazes

The influence of barium oxide on glazes in the SiO ₂-Al ₂O ₃-CaO-MgO-K ₂O system was investigated. Samples were prepared with 0, 2.5, 5 and 7.5 wt% of barium oxide added to this system. The glazes were fired at 1240 °C and the structure and surface properties were determined. Qualitative and quantitative analyses of phase composition, surface properties, structural mid-infrared analysis, and microstructure were performed. Diopside was detected in all glazes as the MgO content was higher than 2.5 wt%. Hyalophane crystals were observed when the BaO content increased to 5 wt%. Mid-infrared studies showed that the appearance of crystalline phases ordered the structure of the glazes; on the other hand, the amorphous phase increased its disorder related to the higher amount of modifying barium cations. The addition of barium oxide did not significantly affect the color of the surface but caused an increase in roughness due to surface crystallization. The microhardness increased with an increased amount of barium in the amorphous phase.