磷灰石型LSO固体电解质的燃烧法多位掺杂及其缺陷增强电导机理研究

Solid electrolyte is the key components of SOFCs.The technology with doping the solid electrolyte for reinforing the electrical performance is the key technology. There are many deficiencies in the traditional doping methods such as the proportioning with raw material can not be controlled accurately, the impurity phase is always present in the products, the size of the crystalline form can not also be controlled, the reaction time is too long and the reaction temperature is too high ect.According to this problems, the combustion method conbined wih the technology of plasma enhanced by MOVCD was used in the project for doping the different sites of apatite type electrolyte LSO.The nitrogen doping of LSO can be realized by the technology of plasma enhanced by MOVCD.Based on the mechanism of conductance reinforcement of doping LSO is not distinct and systemic,the A-site, M-site and O-site of LSO were doped in the project .With the doping activities, the four kinds of point defects which are “interstitial oxygen”、“cation vacancy”、 “defects composite center” and “oxygen vacancy with nitrogen doping” were found and researched.The local refined structure model of the four kinds of point defects were established.The relationship among the conductivity and the lattice constants of LSO with different structure-site doping and the concentration of four kinds of point defects were investigated.The results revealsed four kinds of defect reinforement machnicm as follows :.①.The concentration of interstitial oxygen defect has the positive reinforcement effect;.②.The concentration of cation vacancy defect has the negative reinforcement effect;.③.The concentration of oxygen vacancy defect has the space conductivity reinforcement effect;. The theoretic basis and the technical basis for improving the conductivity of solid electrolyte materials will be provided by the research results in this project.

固体电解质是氧化物燃料电池中的关键部件，掺杂电导增强是其关键技术。针对传统方法在掺杂过程中难以准确配比、有杂质相、尺寸形态不可控、反应时间长、温度高等不足，本项目采用燃烧法（辅以等离子MOCVD氮杂）来实现磷灰石型固体电解质LSO的多位掺杂。基于目前掺杂电导增强机理还不十分清楚，课题通过对LSO 结构中A位、M位、O位等进行三位掺杂，研究其起电导增强作用的"间隙氧"、"阳离子空位"、"缺陷叠合中心"、"氮杂氧空位"等4种点缺陷的特征，建立其局部精细缺陷结构模型；通过对电导率与不同位掺杂的晶格常数及4种点缺陷浓度的关系研究，揭示以①间隙氧缺陷浓度正增强、②阳离子空位浓度负增强、③空间电导增强等‘三效应’为特征的缺陷电导增强机理。研究成果将为固体电解质材料电导率的提高提供理论依据与技术基础。

固体电解质是固体氧化物燃料电池中的关键部件，起着隔离反应气体和输送氧离子的重要作用，其电导性能的大小直接影响着燃料电池的性能。作为一种新型固体电解质材料， La9.33+x(SiO4)6O2+3x/2（LSO）因其特殊的p63/m磷灰石型晶体结构，在中低温下表现出较高的离子电导率和较低的活化能，具有应用于固体氧化物燃料电池电解质的潜力，使得固体氧化物燃料电池在中低温下工作成为可能。. 通过掺杂影响结构，进而提高LSO的电导性能，是可行性较高的研究思路。针对传统方法在掺杂过程中难以准确配比、有杂质相、尺寸形态不可控、反应时间长、温度高等不足，本课题将燃烧法引入到LSO电解质粉体的合成中来，使用较廉价的尿素作为燃料，完善了前驱体的制备工艺，采用尿素-硝酸盐燃烧法（辅以等离子增强MOCVD氮杂）实现了磷灰石型固体电解质LSO的A位、M位、O位的多位掺杂，为其掺杂改性研究提供了新的途径。. 其中A位以不同离子半径的碱土金属为掺杂元素，M位以不同价态的Al3+、Ti4+、V5+为掺杂元素，O位则是以离子半径相近、电负性不同的N 3-作为掺杂元素。. 基于掺杂电导增强机理还不十分清楚，课题通过对LSO 结构中的A位、M位、O位分别进行单位掺杂，系统研究了三种掺杂方式的电导增强作用，在自由氧传导机理和间隙氧传导机理的基础上，建立了“间隙氧”、“阳离子空位”、“缺陷叠合中心”及“氮杂氧空位”4种点缺陷结构模型；通过分析电导率变化与不同位掺杂的晶格常数及4种点缺陷浓度的关系，进一步提出了以“间隙氧缺陷浓度正增强效应”、“阳离子空位浓度负增强效应”以及“空间电导增强效应”为特征的缺陷电导增强机理，丰富了LSO固体电解质材料电导性能的理论基础。

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