【摘要】：固體氧化物燃料電池SOFCs主要由電解質(zhì),陽(yáng)極和陰極三部分關(guān)鍵組件組成。其中固體電解質(zhì)的導(dǎo)電率及其厚度對(duì)SOFCs操作溫度的影響很大,實(shí)際應(yīng)用要求電解質(zhì)的導(dǎo)電率至少大于10-2 S/cm。目前SOFCs的操作溫度較高,這帶來(lái)一系列兼容性與穩(wěn)定性的問(wèn)題,限制了其應(yīng)用。降低SOFCs操作溫度到500°C左右需要新型高性能的氧離子電解質(zhì)。本論文通過(guò)在低對(duì)稱(chēng)的四面體結(jié)構(gòu)體系中,通過(guò)不等價(jià)取代引入間隙氧和氧空位缺陷的方式來(lái)篩選氧離子導(dǎo)體,研究氧離子缺陷在不同結(jié)構(gòu)中穩(wěn)定及遷移機(jī)制,為設(shè)計(jì)和合成新型氧離子導(dǎo)體提供思路和方法。具體研究結(jié)果如下:1.我們?cè)诰哂袑訝罨旌纤拿骟w和四方錐體網(wǎng)絡(luò)結(jié)構(gòu)的硅鈦鋇石Ba2TiSi2O8(BTS)分別用低價(jià)的K+和高價(jià)的La3+取代Ba2+,嘗試引入氧空位和間隙氧,對(duì)BTS材料的不等價(jià)取代的缺陷化學(xué)及其對(duì)離子導(dǎo)電的影響開(kāi)展了研究,結(jié)果表明:K+和La3+對(duì)Ba2+取代溶解度非常有限,BTS層狀結(jié)構(gòu)過(guò)于剛性,無(wú)法獲得高濃度的氧空位和間隙氧缺陷;在Ba2-xKxTiSi2O8-0.5x體系中出現(xiàn)結(jié)晶相Ba2TiSi2O8與玻璃相K2TiSi2O7的物相分離現(xiàn)象;隨著K含量的增加,玻璃相含量增加,樣品的離子電導(dǎo)率提高,但是當(dāng)無(wú)定形玻璃結(jié)晶后,離子電導(dǎo)率下降;Ba2-xKxTiSi2O8-0.5x復(fù)合物相體系中的氧離子導(dǎo)電非常有限;其增強(qiáng)的離子導(dǎo)電歸因于玻璃成分中K+離子導(dǎo)電。純玻璃樣品導(dǎo)電和變溫衍射測(cè)量再現(xiàn)了Ba2-xKxTiSi2O8-0.5x混合物相體系的導(dǎo)電和重結(jié)晶行為。2.我們?cè)诰哂薪惶娴腂a層和混合4-連接的四面體SiO4和平面MO4的多面體網(wǎng)絡(luò)結(jié)構(gòu)的BaCuSi4O10中,嘗試通過(guò)氧化、還原處理和在Ba位用高價(jià)的La3+取代的方法,引入氧缺陷,發(fā)現(xiàn):BaCuSi4O10樣品中存在一定量的一價(jià)銅離子,有氧空位缺陷存在;交流阻抗譜測(cè)量表明陶瓷樣品在950°C的電導(dǎo)率為1.98×10-5S/cm,在高溫下有電極響應(yīng)存在,顯示樣品中存在有限的氧離子導(dǎo)電;無(wú)法通過(guò)在氧氣氣氛中氧化和在碳粉中還原的方法改變樣品中Cu的價(jià)態(tài),從而控制氧缺陷的含量變化;用La3+在Ba2+位高價(jià)取代,難以引入間隙氧,無(wú)法獲得單一物相的固溶體。3.我們合成了系列硅酸鹽玻璃Na2Si2O5、K2Si2O5以及Na2MgSi2O6,進(jìn)行不同氣氛(N2和O2)交流阻抗測(cè)和氧濃差電池測(cè)試,發(fā)現(xiàn):玻璃相Na2Si2O5中同時(shí)存在鈉離子和氧離子導(dǎo)電兩種導(dǎo)電機(jī)理,氧離子導(dǎo)電占主要部分,在O2/玻璃/空氣濃差電池測(cè)量中,600°C下氧離子遷移數(shù)測(cè)量值為0.94,玻璃樣品在650°C的電導(dǎo)率為5.8×10-2 S/cm;K2Si2O5在650°C的電導(dǎo)率為4.0×10-2 S/cm,沒(méi)有明顯的氧離子導(dǎo)電,主要為K+離子導(dǎo)電;Na2MgSi2O6在500°C的電導(dǎo)率為1.7×10-3 S/cm,存在Na+離子導(dǎo)電和有限的氧離子導(dǎo)電;玻璃樣品Na2Si2O5、K2Si2O5結(jié)晶導(dǎo)致電導(dǎo)率下降,而玻璃相Na2MgSi2O6結(jié)晶后電導(dǎo)率上升;精修表明玻璃相Na2MgSi2O6結(jié)晶成分為Na1.74Mg0.865Si1.135O4,在650°C時(shí),電導(dǎo)率升高為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 擄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 擄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 擄C and the conductivity of glass sample is 5.8 脳 10 ~ (-2) S / cm ~ (-2) K _ 2Si _ 2O _ 5 at 650 擄C, which is 4.0 脳 10 ~ (-2) S ~ (-1) 路cm ~ (-1) at 650 擄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 擄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 擄C.
【學(xué)位授予單位】：桂林理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TM911.4

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 張德新,岳慧敏;固體氧化物燃料電池與電解質(zhì)材料[J];武漢理工大學(xué)學(xué)報(bào)(交通科學(xué)與工程版);2003年03期

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本文編號(hào)：2160188