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

Glass-ceramics with off-stoichiometric celsian composition of 50 wt% BaO . 2SiO(2) - 50 wt% BaO . Al2O3. 2SiO(2), (B2S-BA2S) were fabricated and inves tigated for their sintering and crystallization characteristics. (B2S-BA2S) glass powder showed a melting temperature much lowered compared to that of stoichiometric BaO . Al2O3. 2SiO(2) (BA2S) glass powder and high sintering ability. (B2S-BA2S) glass powder containing B2O3, (B2S-BA2S)B and that con taining B2O3 and TiO2, (B2S-BA2S)BT revealed much lowered crystallization p eak temperatures, but rather low sintered density. By applying Kissiger ana lysis to differential thermal analysis (DTA) data activation energy values for crystallization were determined as 265, 195 and 242 kJ/mol, respectivel y for (B2S-BA2S), (B2S-BA2S)B and (B2S-BA2S)BT glasses. X-ray diffraction ( XRD) patterns from all the glass-ceramics crystallized at 1100 degrees C fo r 4 h revealed formation of crystalline phases of beta-BaO . 2SiO(2), monoc elsian and hexacelsian. (B2S-BA2S) glass-ceramics crystallized at 1400 degr ees C for 4 h showed formation of beta-BaO . 2SiO(2) and monocelsian phases with only trace of metastable hexacelsian phase. (C) 2000 Kluwer Academic Publishers.