Preparation And Properties Of Glass-Ceramics In The Li₂O-ZnO-SiO₂ System

As a kind of material of sealing glass, Li2O-ZnO-SiO2 system glass has very important capabilities, such as softening point, high mechanical strength, high thermal expansion coefficient, good thermal and chemical stability, etc. It can be applied in many fields, and get much attentions of scholars both at home and abroad. In this paper, Li2O-ZnO-SiO2 system glass-ceramics were prepared with different additives of ZnO, P2O5, TiO2, and CaF2 in the glassy system. The effects of different contents of additions and the crystallization temperature on the crystallization and properties were investigated by the differential scanning calorimetry(DSC), X-ray diffractometry(XRD), scanning electron microscopy(SEM). The results obtained show that:1. In the Li2O-ZnO-SiO2 system glass-ceramic, the crystallization phases are cristobalite phase, tridymite phase, SiO2 phase and Li2SiZnO4 phase. Nucleating agents of the different types have less effects on the crystallization phases of the glass-ceramic.2. With the increasing of the content P2O5 in the Li2O-ZnO-SiO2 glass, the relative content of precipitated cristobalite phase increases firstly and then decreases. With the effects of cristobalite phase, the thermal expansion coefficient value a also increases firstly and then decreases. The relative content of cristobalite phase is the highest at the addition of P2O5 of 4.0%, and the thermal expansion coefficient value a reaches a maximum value of 16.59×10-6/℃. In the glass-ceramics which the content of P2O5is 5.1%, cristobalite phase is crystallized at 710℃. The thermal expansion coefficient value a increases from 10.86×10-6/℃to 15.36×10-6/℃as the crystallizing temperature change from 535℃to 710℃. 3. With the increasing of the content TiO2 in the LiaO-ZnO-SiO2 glass, the relative content of precipitated cristobalite phase decreases firstly and then increases. With the effects of cristobalite phase, the thermal expansion coefficient value a also decreases firstly and then increases. The relative content of cristobalite phase is the lowest at the addition of TiO2 of 10.3%, and the thermal expansion coefficient value a reaches a minimum value of 8.8×10-6/℃. In the glass-ceramics which the content of TiO2 is 20.6%, cristobalite phase is crystallized at 700℃. The thermal expansion coefficient value a increases from 9.95×10-6/℃to 13.57×10-6/℃as the crystallizing temperature change from 609℃to 700℃.4. With the increasing of the content CaF2 in the Li2O-ZnO-SiO2 glass, the relative contents of precipitated cristobalite phase decreases at all. With the effects of cristobalite phase, the thermal expansion coefficient value a also decreases at all. The relative content of cristobalite phase is the lowest at the addition of CaF2 of 16.0%, and the thermal expansion coefficient value a reaches a minimum value of 7.5×10-6/℃.In the glass-ceramics which the content of CaF2 is 4.0%, cristobalite phase is crystallized at 706℃. The thermal expansion coefficient value a increases from 7.45×10-6/℃to 8.31×10-6/℃as the crystallizing temperature change from 650℃to 700℃.5. With the increasing of the content ZnO in the Li2O-ZnO-SiO2 glass, the relative contents of precipitated cristobalite phase increases firstly and then decreases. With the effects of cristobalite phase, the thermal expansion coefficient value a increases firstly and then decrease. The relative content of cristobalite phase is the highest at the addition of ZnO of 26.7%, and the thermal expansion coefficient value a reaches a maximum value of 16.59×10-6/℃. In the glass-ceramics which the content of ZnO is 20.40%, cristobalite phase iscrystallized at 710℃. The thermal expansion coefficient value a increases from 11.65×10-6/℃to 18.45×10-6/℃as the crystallizing temperature change from 535℃to 710℃.