Effect of ZrO2 on crystallization and phase transformation in low-temperature processed BaO-Al2O3-SiO2 glass-ceramics

BaO-Al2O3-SiO2(BAS) glass-ceramics with stoichiometric and off-stoichiometric celsian composition were fabricated, doped with B2O3 for melting and sintering. Crystallization and phase transformation characters of two groups of BAS glass-ceramics with and without ZrO2 were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and dilatometry. Results show that for both BAS glasses, the sintering temperature is lower than 850 degrees C and crystallization peak temperature is lower than 900 degrees C. The crystallization characteristic of hexacelsian in each sample is bulk nucleation and three-dimensional growth because Avrami exponent is 2.8-3.9. The crystallization characteristic of monocelsian in the sample doped with ZrO2 is surface nucleation and one-dimensional growth because Avrami exponent is 0.95, while it is bulk nucleation and three-dimensional growth because Avrami exponent is about 3.0 in the sample without nucleation agent. It reveals that crystallization peak temperature and activation energy get lower in stoichiometric BAS glass-ceramics doped with ZrO2, while the crystallization peak temperature get higher in off-stoichiometric BAS glass-ceramics doped with ZrO2. Stoichiometric BAS glass-ceramics doped with ZrO2 crystallized at 850 degrees C for 12h is completely transformed into monocelsian. Monocelsian will not be detected in off-stoichiometric BAS doped with ZrO2 crystallized at 850 degrees C for 100h.