系列具有四面体网络结构的新型氧离子导体的探索
发布时间：2018-08-02 17:42
【摘要】：固体氧化物燃料电池SOFCs主要由电解质,阳极和阴极三部分关键组件组成。其中固体电解质的导电率及其厚度对SOFCs操作温度的影响很大,实际应用要求电解质的导电率至少大于10-2 S/cm。目前SOFCs的操作温度较高,这带来一系列兼容性与稳定性的问题,限制了其应用。降低SOFCs操作温度到500°C左右需要新型高性能的氧离子电解质。本论文通过在低对称的四面体结构体系中,通过不等价取代引入间隙氧和氧空位缺陷的方式来筛选氧离子导体,研究氧离子缺陷在不同结构中稳定及迁移机制,为设计和合成新型氧离子导体提供思路和方法。具体研究结果如下:1.我们在具有层状混合四面体和四方锥体网络结构的硅钛钡石Ba2TiSi2O8(BTS)分别用低价的K+和高价的La3+取代Ba2+,尝试引入氧空位和间隙氧,对BTS材料的不等价取代的缺陷化学及其对离子导电的影响开展了研究,结果表明:K+和La3+对Ba2+取代溶解度非常有限,BTS层状结构过于刚性,无法获得高浓度的氧空位和间隙氧缺陷;在Ba2-xKxTiSi2O8-0.5x体系中出现结晶相Ba2TiSi2O8与玻璃相K2TiSi2O7的物相分离现象;随着K含量的增加,玻璃相含量增加,样品的离子电导率提高,但是当无定形玻璃结晶后,离子电导率下降;Ba2-xKxTiSi2O8-0.5x复合物相体系中的氧离子导电非常有限;其增强的离子导电归因于玻璃成分中K+离子导电。纯玻璃样品导电和变温衍射测量再现了Ba2-xKxTiSi2O8-0.5x混合物相体系的导电和重结晶行为。2.我们在具有交替的Ba层和混合4-连接的四面体SiO4和平面MO4的多面体网络结构的BaCuSi4O10中,尝试通过氧化、还原处理和在Ba位用高价的La3+取代的方法,引入氧缺陷,发现:BaCuSi4O10样品中存在一定量的一价铜离子,有氧空位缺陷存在;交流阻抗谱测量表明陶瓷样品在950°C的电导率为1.98×10-5S/cm,在高温下有电极响应存在,显示样品中存在有限的氧离子导电;无法通过在氧气气氛中氧化和在碳粉中还原的方法改变样品中Cu的价态,从而控制氧缺陷的含量变化;用La3+在Ba2+位高价取代,难以引入间隙氧,无法获得单一物相的固溶体。3.我们合成了系列硅酸盐玻璃Na2Si2O5、K2Si2O5以及Na2MgSi2O6,进行不同气氛(N2和O2)交流阻抗测和氧浓差电池测试,发现:玻璃相Na2Si2O5中同时存在钠离子和氧离子导电两种导电机理,氧离子导电占主要部分,在O2/玻璃/空气浓差电池测量中,600°C下氧离子迁移数测量值为0.94,玻璃样品在650°C的电导率为5.8×10-2 S/cm;K2Si2O5在650°C的电导率为4.0×10-2 S/cm,没有明显的氧离子导电,主要为K+离子导电;Na2MgSi2O6在500°C的电导率为1.7×10-3 S/cm,存在Na+离子导电和有限的氧离子导电;玻璃样品Na2Si2O5、K2Si2O5结晶导致电导率下降,而玻璃相Na2MgSi2O6结晶后电导率上升;精修表明玻璃相Na2MgSi2O6结晶成分为Na1.74Mg0.865Si1.135O4,在650°C时,电导率升高为5.0×10-1 S/cm。
[Abstract]:Solid oxide fuel cell (SOFC) SOFCs consists of three key components: electrolyte, anode and cathode. The conductivity of solid electrolyte and its thickness have great influence on the operating temperature of SOFCs. The conductivity of electrolyte is required to be more than 10-2 S / cm in practical application. At present, the operating temperature of SOFCs is high, which brings a series of compatibility and stability problems, which limits its application. A new type of high performance oxygen ion electrolyte is needed to reduce the operating temperature of SOFCs to about 500 掳C. In this paper, oxygen ion conductors are screened by replacing gap oxygen and oxygen vacancy defects in low symmetry tetrahedron structures, and the mechanism of oxygen ion defects stability and migration in different structures is studied. It provides ideas and methods for the design and synthesis of new oxygen ion conductors. The specific research results are as follows: 1. In Ba2TiSi2O8 (BTS) with layered mixed tetrahedron and tetragonal pyramidal network structure, we try to introduce oxygen vacancy and interstitial oxygen to replace Ba2 with low price K and high valence La3, respectively. The defect chemistry and its effect on ionic conductivity of BTS materials are studied. The results show that the solubility of Ba2 substitution is very limited and the layered structure of Ba2 is too rigid to obtain high concentration of oxygen vacancy and interstitial oxygen defects. The phase separation of crystalline phase Ba2TiSi2O8 and glass phase K2TiSi2O7 appeared in Ba2-xKxTiSi2O8-0.5x system. With the increase of K content, the content of glass phase increased and the ionic conductivity of the sample increased, but when amorphous glass crystallized, The ionic conductivity of Ba2-xKxTiSi2O8-0.5x complex system is very limited, and the enhanced ionic conductivity is attributed to K ion conduction in glass composition. The conductivity and recrystallization behavior of the Ba2-xKxTiSi2O8-0.5x mixture system were reconstructed by conducting and temperature-varying diffraction measurements of pure glass samples. We try to introduce oxygen defects in BaCuSi4O10 with alternate Ba layer and polyhedron network structure of mixed 4-connected tetrahedron SiO4 and plane MO4 by oxidation, reduction treatment and substitution of high price La3 at Ba site. It is found that there is a certain amount of monovalent copper ion and oxygen vacancy defect in the sample of 1: BaCuSi4O10, the conductivity of ceramic sample at 950 掳C is 1.98 脳 10 ~ (-5) S / cm, and the electrode response exists at high temperature, indicating that there is limited oxygen ion conduction in the sample. The valence state of Cu in the sample can not be changed by oxidation in oxygen atmosphere and reduction in carbon powder to control the change of the content of oxygen defect, and it is difficult to introduce interstitial oxygen with La3 at Ba2 site, and the solid solution. 3 of single phase can not be obtained. A series of silicate glasses Na _ 2Si _ 2O _ 5 K _ 2Si _ 2O _ 5 and Na _ 2MgSi _ 2O _ 6 have been synthesized. Ac impedance measurements and oxygen concentration cell measurements in different atmospheres (N _ 2 and O _ 2) have been carried out. It is found that both sodium ion and oxygen ion conduction mechanism exist in glass phase Na2Si2O5. Oxygen ion conduction is the main part. The oxygen ion migration number is 0.94 at 600 掳C and the conductivity of glass sample is 5.8 脳 10 ~ (-2) S / cm ~ (-2) K _ 2Si _ 2O _ 5 at 650 掳C, which is 4.0 脳 10 ~ (-2) S ~ (-1) 路cm ~ (-1) at 650 掳C. there is no obvious oxygen ion conduction. The main conductivity of Na _ 2MgSi _ 2O _ 6 is 1.7 脳 10 ~ (-3) S / cm at 500 掳C, there is Na ion conduction and limited oxygen ion conduction, the crystallization conductivity of Na _ 2Si _ 2O _ 5 / K _ 2Si _ 2O _ 5 decreases, but the conductivity of glass phase Na2MgSi2O6 increases after crystallization. Refinement shows that the crystalline composition of glass phase Na2MgSi2O6 is Na1.74Mg0.865Si1.135O4, and the conductivity increases to 5.0 脳 10-1 S / cm at 650 掳C.
【学位授予单位】：桂林理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM911.4
本文编号：2160188
[Abstract]:Solid oxide fuel cell (SOFC) SOFCs consists of three key components: electrolyte, anode and cathode. The conductivity of solid electrolyte and its thickness have great influence on the operating temperature of SOFCs. The conductivity of electrolyte is required to be more than 10-2 S / cm in practical application. At present, the operating temperature of SOFCs is high, which brings a series of compatibility and stability problems, which limits its application. A new type of high performance oxygen ion electrolyte is needed to reduce the operating temperature of SOFCs to about 500 掳C. In this paper, oxygen ion conductors are screened by replacing gap oxygen and oxygen vacancy defects in low symmetry tetrahedron structures, and the mechanism of oxygen ion defects stability and migration in different structures is studied. It provides ideas and methods for the design and synthesis of new oxygen ion conductors. The specific research results are as follows: 1. In Ba2TiSi2O8 (BTS) with layered mixed tetrahedron and tetragonal pyramidal network structure, we try to introduce oxygen vacancy and interstitial oxygen to replace Ba2 with low price K and high valence La3, respectively. The defect chemistry and its effect on ionic conductivity of BTS materials are studied. The results show that the solubility of Ba2 substitution is very limited and the layered structure of Ba2 is too rigid to obtain high concentration of oxygen vacancy and interstitial oxygen defects. The phase separation of crystalline phase Ba2TiSi2O8 and glass phase K2TiSi2O7 appeared in Ba2-xKxTiSi2O8-0.5x system. With the increase of K content, the content of glass phase increased and the ionic conductivity of the sample increased, but when amorphous glass crystallized, The ionic conductivity of Ba2-xKxTiSi2O8-0.5x complex system is very limited, and the enhanced ionic conductivity is attributed to K ion conduction in glass composition. The conductivity and recrystallization behavior of the Ba2-xKxTiSi2O8-0.5x mixture system were reconstructed by conducting and temperature-varying diffraction measurements of pure glass samples. We try to introduce oxygen defects in BaCuSi4O10 with alternate Ba layer and polyhedron network structure of mixed 4-connected tetrahedron SiO4 and plane MO4 by oxidation, reduction treatment and substitution of high price La3 at Ba site. It is found that there is a certain amount of monovalent copper ion and oxygen vacancy defect in the sample of 1: BaCuSi4O10, the conductivity of ceramic sample at 950 掳C is 1.98 脳 10 ~ (-5) S / cm, and the electrode response exists at high temperature, indicating that there is limited oxygen ion conduction in the sample. The valence state of Cu in the sample can not be changed by oxidation in oxygen atmosphere and reduction in carbon powder to control the change of the content of oxygen defect, and it is difficult to introduce interstitial oxygen with La3 at Ba2 site, and the solid solution. 3 of single phase can not be obtained. A series of silicate glasses Na _ 2Si _ 2O _ 5 K _ 2Si _ 2O _ 5 and Na _ 2MgSi _ 2O _ 6 have been synthesized. Ac impedance measurements and oxygen concentration cell measurements in different atmospheres (N _ 2 and O _ 2) have been carried out. It is found that both sodium ion and oxygen ion conduction mechanism exist in glass phase Na2Si2O5. Oxygen ion conduction is the main part. The oxygen ion migration number is 0.94 at 600 掳C and the conductivity of glass sample is 5.8 脳 10 ~ (-2) S / cm ~ (-2) K _ 2Si _ 2O _ 5 at 650 掳C, which is 4.0 脳 10 ~ (-2) S ~ (-1) 路cm ~ (-1) at 650 掳C. there is no obvious oxygen ion conduction. The main conductivity of Na _ 2MgSi _ 2O _ 6 is 1.7 脳 10 ~ (-3) S / cm at 500 掳C, there is Na ion conduction and limited oxygen ion conduction, the crystallization conductivity of Na _ 2Si _ 2O _ 5 / K _ 2Si _ 2O _ 5 decreases, but the conductivity of glass phase Na2MgSi2O6 increases after crystallization. Refinement shows that the crystalline composition of glass phase Na2MgSi2O6 is Na1.74Mg0.865Si1.135O4, and the conductivity increases to 5.0 脳 10-1 S / cm at 650 掳C.
【学位授予单位】：桂林理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM911.4
【参考文献】
相关期刊论文 前1条
1 张德新,岳慧敏;固体氧化物燃料电池与电解质材料[J];武汉理工大学学报(交通科学与工程版);2003年03期
，本文编号：2160188
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