【作者】 刘荣辉；

【导师】 王华； 马文会；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2006， 硕士

【摘要】 固体氧化物燃料电池（SOFC）因具有高效、环境友好等优点,被视为解决二十一世纪能源问题的重要技术之一。电池工作温度过高和阳极积碳现象是困扰SOFC发展的两个主要问题。温度过高会造成电池密封困难、电池构件不匹配、性能衰减、工作寿命短、制备成本高等诸多问题,阳极积碳现象同样会引起电池性能的迅速衰减和使用寿命的降低。因此,开发在中低温范围内具有高离子电导率的电解质材料,以及研制适用于在中温条件下工作并能有效防止积碳现象发生的阳极材料有着十分重要的意义。 La_1-xSr_xGa_1-yMg_yO₃（LSGM）在中低温（850℃以下）范围内,很宽的氧分压下具有较高的离子电导率,可作为中温固体氧化物燃料电池（ITSOFC）用电解质备选材料。但是单一相的LSGM材料很难制备,特别是采用固相法制备LSGM时,原料的化学配比不精确、高温烧结的过程中原料组分（如Ga）的挥发、以及不当的实验操作等因素很容易产生SrLaGa₃O₇、SrLa（GaO₄）等杂相。杂相对材料的结构、化学稳定性和导电性能都会产生十分消极的影响。所以,本文的研究内容之一就是通过改进实验条件,制备出具有单一钙钛矿相的LSGM,并对其性能进行研究。 LaCrO₃基材料被认为最有希望解决阳极积碳现象的阳极材料之一。在这种材料中,A、B位元素有着不同的作用。A位的La元素可以稳定材料的结构,部分的Sr取代La可以提高材料的电导性能;B位的Mn元素可以提高材料的催化性能,Cr元素不仅可以提高材料的稳定性,提高其对含硫材料的容忍性,还可望减少或消除阳极积碳现象。所以,本文另一个重要的研究内容是合成La_1-xSr_xCr_1-yMn_yO_3-δ（LSCM）材料,并将其作为阳极材料进行性能研究。 由LSGM合成实验研究发现:反应物料经1000℃烧结后,即可产生钙钛矿相;随温度的升高,材料中的杂相逐渐减少;1300℃下烧结24h后,材料中仅含有少量杂相;经1450℃和1480℃烧结24h后,均得到单一相的LSGM。LSGM样品的电导率随温度的升高而升高,而且性能稳定;在800℃材料的离子电导率为1.2×10^-2S/cm,与传统电解质YSZ、硝酸盐—柠檬酸燃烧法及柠檬酸盐法制备的LSGM电解质在同一温度下的电导更多还原

【Abstract】 Solid oxide fuel cell （SOFC） has many advantages of high efficiency, low emissions of sulfur, nitrogen oxides and hydrocarbon pollutants, which is considered to be one of the key techniques resolving the energy problems in the 21ths. High operating temperature and carbon deposition in anode are the two main problems hampering the development of SOFC. The high operating temperature results in numerous disadvantages such as the difficulties of sealing SOFC, the deterioration of thermodynamic compatibility between electrodes and electrolyte components, the emerging of chemical reactions at the boundary of electrodes and electrolyte, the increase of SOFC fabrication cost, and the deduction of long-term. The carbon deposition can result in the deterioration of cell capability in a short time. So, it is necessary to develop novel electrolyte and anode materials to resolve the above problems. The electrolyte material should have highly pure ionic conductivity at the low and intermediate temperatures （below 850℃）, the anode material should have high ion-electronic conductivity at the low and intermediate temperatures and which can reduce or avoid the carbon deposition in anode.La_1-xSr_xGa_1-yMg_yO_3-δ（LSGM） material has high ionic conductivity over the large range of oxygen partial pressure at the low and intermediate temperatures, which is excellent electrolyte candidate for intermediate temperature solid oxide fuel cell（ITSOFC）.But it is difficult to synthesize LSGM electrolyte material with a single phase, with low-conductivity phase such as SrLaGa₃O₇ and SrLa(GaO₄ forming for inappropriate operations when using solid-state reaction method especially. These impurities have very bad impacts on the structure, chemical stability and conductivity of LSGM. One of our tasks is to modify experimental condition and prepare single-phase LSGM.LaCrO₃-based material is considered to be one of anode materials which can resolve carbon deposition. The elements in A-site and B-site have different impacts on the performance of the material. For example, the La element can heighten the stability of material, the conductivity will increase when partial La is substituted by Sr. The material has excellent catalytic property for the Mn element in B-site and goodtolerance to sulfur properties for the Cr element in B site. So, another task is synthesizing and Characterization Lai.xSrxCri.yMny03.5（LSCM） as anode material.According to the LSGM preparation experimental, the following conclusions are obtained. Perovskite phase began to form after the precursors material was sintered at 1000"C. A small amount of SrLaGa3C>7 was formed when sintering at 1300°C. A single-phase perovskite was both identified after sintering at 1450°C and 1480 °C for 24h, respectively. The ionic conductivity of LSGM was stable and increased with the temperature increasing. The 1.2xlO"2S/cm conductivity in 800"C was similar to that of samples measured by other researchers. The sintering temperature, density of sample and grain boundary resistance has big impacts on the ionic conductivity of LSGM.According to the LSGM synthesis experimental, one can draw the following conclusions. Perovskite phase began to form after the precursors material was sintered at 1000°C. Many impurities such as LaiCh and Sri.sLao.sMnC^ were formed at the low temperatures. A single-phase perovskite was both identified after sintering at 1250’C and 1350 °C for 15h, respectively. The grain and grain boundary resistances decreased and the ionic conductivity increased with the temperature increasing over the temperature range of 300⁸00°C. But the grain boundary resistances were big even at high temperature. The electronic conductivity increased linely with temperature increasing over the range of 300⁶50°C, which increased more quickly when the temperature is over 650°C and was about 1.5S/cm at 850"C.Moreover, the compatibilities between LSGM and LSCM and novel LSFC cathode materials were studied in order to promote the application of the above three materials. They have good chemical capability between LSGM and LSMC and LSFC, but a little impurity such as La2C?3, La4Ga2C>9 emerged resulted from the evaporation of the element Ga in LSGM material in the heating process of the mixed powder with LSGM and LSMC at 1200°C for 15h. Porous LSCM anode film with a 10um thickness was obtained in LSGM pellet, and anode film was well cohered on the LSGM electrolyte substrate. It shows a good thermodynamic capability between LSGM and LSCM. The desired LSFC cathode film wasn’t obtained in LSGM pellet. It shows that they haven’t good thermodynamic capability between LSGM and LSFC.The single cell was fabricated using LSCM, LSFM and LSGM as anode, cathode and electrolyte materials, respectively. The open circuit voltage is about 1.06V at850°C when the flux of hydrogen is 0.5L/min and that of air is 0.2L/min, which is similar to the theoretical electromotive force. It shows that the sealing of cell is very good. The max powder density is about 25mW/cm2 at 850"C, which is relatively small for the big boundary resistances between electrodes and electrolyte and current collectors. The fabrication technique must be modified in the future in order to get better powder density.更多还原