Investigation of the effect of BaO-Al2O3 variations for BAS glass-ceramic glaze: Insights into thermal, phase, microstructural and surface features

Abstract

This study aims to investigate the phase transformation, thermal behavior, microstructure evaluation and surface feature of the barium aluminosilicate (BAS) glass-ceramic glaze by changing barium oxide (BaO) and aluminium oxide (Al2O3) amounts. Differential thermal analysis (DTA) analysis showed that the first crystallization occurred at 800 °C and referred to the celsian formation, and crystallization temperature increased as Al2O3 content increased. Characteristic temperature and high thermal viscosity behavior was examined by hot-stage microscope analysis and the Vogel–Fulcher–Tammann (VFT) equation. X-ray diffraction (XRD) analysis showed that replacing Al2O3 with BaO resulted in an enhanced celsian (Ba0.8Al1.6Si2.4O8) phase. On the other hand, increasing Al2O3 content promoted the corundum (α-Al2O3) phase. The glassy and crystalline phase amount was determined by using Rietveld method. Field Emission Scanning Electron Microscope (FESEM) observations showed rectangular, strip-like celsian crystals, unshaped corundum crystals and porous microstructure. Surface roughness and the height distribution of surfaces were supported by 3D topographic mapping and determined according to ISO 4287. The highest BaO-contained R1 exhibits lower peaks with 190 µm and valleys with 80 µm, on the contrary, the highest Al2O3-contained R5 has high peaks with 252.7 µm, and deep valleys with 150 µm. Finer celsian crystals and lowest surface roughness ensured the cleanability of the surface and resulted in Class 5 according to ISO 10545-14. When Al2O3 content increased by 30 wt% and above, cleanability began to weaken, resulting in Class 1 and Class 2. The surface has become opaque with an increase in the Al2O3 content.