钐掺杂氧化铈-碳酸盐复合电解质的优化和
电性能研究
什么是embaheicStudy on electrical properties and
optimization of samarium doped
ceria-carbonate composite electrolyte
学科专业：工业催化hotstuds
www cnn com常用英语谚语研究生：田力
指导教师：李永丹教授
天津大学化工学院
二零一三年五月
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中文摘要
本文以提高钐掺杂氧化铈-碳酸盐复合电解质的电性能为目的，从优化复合电解质出发，制备了三种新型复合电解质材料。通过XRD、SEM、TG-DTA、交流阻抗谱、直流四电极等方法考察了复合电解质的不同制备方法和不同比例的晶型结构、形貌和电性能，并与传统的复合电解质进行了比较分析。
第二章采用碳酸钠共沉淀法制备出了Ce0.8Sm0.15Sr0.05O2-δ（SSDC）、SSDC/Na2CO3（NaSSDC）复合电解质粉体，考察了前驱体的处理温度对复合电解质的电导率的影响，并用交流阻抗谱法和直流四电极法比较了NaSSDC复合电解质和SSDC的电导率。结果表明，SSDC和NaSSDC的峰型与纯CeO2一致，Na2CO3以无定形态存在。800 o C煅烧获得的材料电导率最高。碳酸钠促进了O2-和H+传导，同时抑制了SSDC在还原气氛下的电子电导。
第三章采用草酸盐共沉淀法制备了Ce0.78Sm0.2Sr0.02O2-δ（SSDC）粉体，与30 wt.% (Li0.52Na0.48)2CO3混合得到SSDC-30LN复合电解质。以同样的制备方法得到SDC、SDC-30LN以作对比。用直流四电极法比较了四种材料的O2-和H+的电导率。结果表明，SDC、SDC-30LN、SSDC和SSDC-30LN均为立方萤石结构，没有其他峰出现。共掺杂技术提高了氧空位浓度，降低了SDC的活化能，促进了O2-的传导；碳酸盐相能促进H+和O2-的传导；氧化铈相和碳酸盐相形成的两相界面对H+电导有促进作用。此外，以NiO为阳极、LiNiO2为阴极，用三层共压共烧工艺制备了SSDC-30LN复合电解质基单电池。考察了单电池在500~650 o C时的输出性能。分析了阴极气中是否含有CO
对电池输出功率的影响。
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第四章采用固相反应法制备Er0.4Bi1.6O3（ESB）粉体，草酸共沉淀法制备SDC 粉体，用固相混合法得到不同比例的ESB-SDC-LN复合电解质。通过直流四电极法测试，分别考察了ESB含量和碳酸盐含量对氧离子、质子传导的影响。复合电解质保持了萤石结构，三者之间没有相互反应。SEM显示随着碳酸盐含量的降低，陶瓷相和碳酸盐相的均匀度提高。复合电解质的O2-和H+的电导率电导率均随碳酸盐的含量的增加而增加，也随ESB的增加而稍有提高。说明熔融碳酸盐能促进两种离子传导，ESB能促进O2-传导，两相界面促进H+传导。
关键词：掺杂氧化铈碳酸盐复合电解质质子传导氧离子传导固体氧化物燃料电池
ABSTRACT
爱情定义In order to improve electrical properties of samarium doped ceria-carbonate, three new types of composite electrolyte materials are synthesized in this work through optimization of SDC-carbonate. XRD, SEM, TG-DTA, EIS and D.C. four-probe techniques were applied to characterize the microstructure, morphology and electrical performance of new materials.
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In chapter 2, Ce0.8Sm0.15Sr0.05O2-δ(SSDC) and SSDC/Na2CO3(NaSSDC) powders were prepared by coprecipitation technique using sodium carbonate as precipitant. The effects of calcination temperature of precursors on the conductivity of the composite electrolytes were examined. The conductivities of SSDC and NaSSDC were compared through EIS and D.C. four-probe method. SSDC and NaSSDC diffraction patterns are same as tho of the pure ceria, Na2CO3is amorphously distributed. The results showed that the highest conductivity was obtained after sintered at 800 o C. Sodium carbonate not only promotes O2- and H+ conduction, but also suppress the electronic conduction.
In chapter 3, Ce0.78Sm0.2Sr0.02O2-δ(SSDC) powders were synthesized through oxalate coprecipitation route. Then 30wt% binary eutectic salt ((Li0.52Na0.48)2CO3) was added to form SSDC-30LN composite electrolyte. SDC and SDC-30LN powders were prepared by the same method for comparison. The O2-and H+conductivities were compared by D.C. four-probe technique. The results showed that SDC, SDC-30LN, SSDC and SSDC-30LN all have cubic fluorite-type structure, no extra peaks were obrved. Co-doping technique enhances the amount of oxygen vacancies, decreas the activation energy of SDC and facilitates O2- conduction. Carbonate pha improves both H+ and O2- conductivities. The interface between carbonate and ceria can promote th
e H+conduction. What’s more, a single fuel cell bad on SSDC-30LN composite electrolyte was fabricated with a tri-layer co-pressing technique, using NiO as anode and LiNiO2 as cathode. The performance of the fuel cell was investigated at 500~650 o C. The effect of CO2supply in cathode side on performance of cell was also studied.
In chapter 4, Er0.4Bi1.6O3(ESB) was prepared through solid state reaction route, and SDC was synthesized by oxalate coprecipitation method. Then ESB-SDC-LN composite electrolytes with different composition were formed by mixing oxides method. Composite electrolytes retains fluorite structure, and there are no reactions
among SDC, ESB and carbonate. The influences of the amount of ESB and carbonate on H+ and O2- conductivities were respectively studied by D.C. four probe method. SEM showed that the distribution of the two phas incread with the decrea of the amount of the carbonate. The H+ and O2- conduction enhanced with the increa of carbonate or ESB, which indicated that carbonate favored H+and O2-conduction, ESB benefited O2-conductivity, and the interface of two phas improved H+ conduction.
KEY WORDS：Doped ceria, Carbonate, Composite electrolyte, Proton conduction, Oxygen ion conduction, Solid oxide fuel cell
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