Sintering and crystallization of off-stoichiometric SrO•Al2O3•2SiO2 glasses

Grass-ceramics with the celsian-corundum binary join composition of 88.8 wt% SrO . Al2O3. 2SiO(2) -11.2 wt% Al2O3, (SA2S-A), were fabricated by pressureless sintering and investigated for their sintering and crystallization behaviors. The (SA2S-A) glass powder showed crystallization peak and melting temperatures of similar to 1059 and 1550 degrees C, respectively and high sintering ability. The (SA2S-A) glass powders containing B2O3, (SA2S-A)B and those containing B2O3 and TiO2, (SA2S-A)BT showed lowered crystallization peak temperatures of 1033 and 997 degrees C, respectively. By applying Kissiger analyses to the DTA data of the (SA2S-A), (SA2S-A)B and (SA2S-A)BT glass powders, the activation energy values for crystallization were determined as 488, 370 and 333 kJ/mol, respectively. The Ozawa analyses on the DTA data gave the Avrami parameter values at 1.2, 1.1 and 1.9, respectively for the (SA2S-A), (SA2S-A)B and (SA2S-A)BT glass powders. The x-ray diffraction (XRD) patterns of the (SA2S-A) glass-ceramics, crystallized at 1100 degrees C for 4 h, showed formation of both the monocelsian and hexacelsian phases. The (SA2S-A)B and (SA2S-A)BT glass-ceramics crystallized at 1100 degrees C for 1 h, showed formation of the phase-pure monocelsian and did not show any evidence of the hexacelsian formation prior to the monocelsian formation. (C) 2000 Kluwer Academic Publishers.