Preparation And Sintering Behaviors Of B₂O₃-SiO₂-BaO-ZnO System Glass Powder

In recent years, the rapid development of lead-free glass, especially borosilicate glass, with its good thermal and structural stability, has been fairly widely used in terms of the solid oxide fuel cell's sealing. In order to limit the use of PbO in the glass system, researchers found that BaO, ZnO can be used as a network modifier replacing the role of PbO in the glass system, and have prepared a new kind of glass sealants with low glass transition temperature. However, adding a large number of network modifier will promote the glass crystallization during the process of sintering densification, which will greatly influence the sintering characteristics and the physicochemical property. In order to prevent the phenomenon of crystallization, this paper adopted the following measures to inhibit the B2O3–SiO2–BaO–ZnO and B2O3–SiO2–BaO–ZnO–Al2O3 glass samples crystallization in the process of sintering densification:Fixed B2O3: SiO2=5: 1, the mole ratio between BaO and ZnO was adjusted to get the best matching. The effects of Ba O and ZnO content on the structures, thermal properties and sintering behaviors of the B2O3–SiO2–ZnO–BaO glass were investigated in detail. The experiments showed that the structural changes of the glasses as well as the changes in the properties of the glasses were influenced by the function of BaO content. As the content of BaO increased, both the glass transition temperature and crystallization temperature decreased. What's more, the damage to the stability of glass network structure could not be ignored when the Ba O content at a high degree. The content of ZnO being too high would also hinder the sintering process. Thus, the glass with 20 mol% BaO was the most stable one. What's more, the crystallization phenomenon would not happen when the samples' sintering density reaches the maximum value.Al2O3 were added based on the original system, fixed B2O3: SiO2: ZnO=5: 1: 1, The effects of Al2O3 content on the structures, thermal properties and sintering behaviors of the B2O3–SiO2–ZnO–BaO–Al2O3 glass were investigated in detail. The results of investigation showed that the introduction of Al2O3 caused the conversion of [BO3] units to [BO4] units. As the same time, because of the existence of Al2O3, the tendency of phase separation and the phenomenon of crystallization would be inhibited. The stability of the glass improved first and then decreased as Al2O3 increased from 1 to 7 mol%, the glass with 5 mol% Al2O3 being the most stable one. Too much Al2O3 would decrease the stability of the specimens. For this reason above all, Al2O3 acted as a network former at larger concentrations and then cut off [BO4] to replaces B3+ and Si4+ in the glass network as well as formed another structure with oxygen ions in tetrahedral coordination. Above all, the focus of this thesis was all on lower sealing temperature materials what was suitable for SOFC sealing.