Sintering and crystallization of off-stoichiometric BaO·Al2O3·2SiO2 glasses

Glass-ceramics with off-stoichiometric celsian composition of 50 wt% BaO·2SiO2 – 50 wt% BaO·Al2O3·2SiO2, (B2S-BA2S) were fabricated and investigated for their sintering and crystallization characteristics. (B2S-BA2S) glass powder showed a melting temperature much lowered compared to that of stoichiometric BaO·Al2O3·2SiO2 (BA2S) glass powder and high sintering ability. (B2S-BA2S) glass powder containing B2O3, (B2S-BA2S)B and that containing B2O3 and TiO2, (B2S-BA2S)BT revealed much lowered crystallization peak temperatures, but rather low sintered density. By applying Kissiger analysis to differential thermal analysis (DTA) data activation energy values for crystallization were determined as 265, 195 and 242 kJ/mol, respectively for (B2S-BA2S), (B2S-BA2S)B and (B2S-BA2S)BT glasses. X-ray diffraction (XRD) patterns from all the glass-ceramics crystallized at 1100°C for 4 h revealed formation of crystalline phases of β-BaO·2SiO2, monocelsian and hexacelsian. (B2S-BA2S) glass-ceramics crystallized at 1400°C for 4 h showed formation of β-BaO·2SiO2 and monocelsian phases with only trace of metastable hexacelsian phase.