材料期刊网

为开发新型高性能中温固体氧化物燃料电池阴极材料,采用改进的固相法制备了Sr~(2+)、Ca~(2+)与Fe~(3+)多元掺杂LaCoO_3基稀土复合氧化物La_(0.8) Sr_(0.1) Ca_(0.1) Co_(0.7) Fe_(0.3) O_(2.9)(LSCCF81173)和La_(0.7) Sr_(0.2) Ca_(0.1) Co_(0.8) Fe_(0.2) O_(2.85)(LSCCF72182).利用EDS、XRD、TG-DTA、SEM及热膨胀法等技术,对制备样品的化学成分、物相结构、形成过程、显微组织及热膨胀系数等进行分析,并采用直流四端子法测量样品在25～850℃的混合电导率.XRD和SEM分析表明,经1200℃烧结,LSCCFS1173和LSCCF72182样品均具有单一的菱方钙钛矿相和孔隙尺寸与分布较均匀的多孔结构;EDS结果证实,制备的样品中基本不合其他杂质元素;在25～500 ℃较低温度区间,混合电导率与温度的关系近似为直线,说明较低温阶段样品的导电行为符合小极化子导电机制,且具有较低的导电活化能(E_a=0.075 84 eV和0.077 98 eV);Ca~(2+)、Fe~(3+)的共同掺杂有利于降低其热膨胀系数,改善与电解质的热匹配性,并对其原因进行了初步分析.

In order to develop novel cathode materials with high performance for intermediate temperature solid oxide fuel cells (SOFC), Sr~(2+)、 Ca~(2+) and Fe~(3+)-doping LaCoO_3-based rare earth composite oxides La_(0.8) Sr_(0.1) Ca_(0.1) Co_(0.7) Fe_(0.3) O_(2.9) (LSCCF81173) and La_(0.7) Sr_(0.2) Ca_(0.1) Co_(0.8) Fe_(0.2) O_(2.85) (LSCCF72182) were prepared by improved solid reaction method. The composition, phase structure, forming process, microstructure and thermal expansion coefficient(TEC) of the samples were analyzed by means of EDS, XRD, TG-DTA, SEM and thermo-dilatometry. The electrical conductivity of the samples was measured by DC four-probe technique in the range of 25 ～ 850 ℃. The single phase materials of rhombohedral perovskite-type and porous structure are formed after sintering in air at 1200 ℃ according to XRD patterns and SEM photographs of LSCCF81173 and LSCCF72182. EDS analysis results show that the impurity elements are not found in the synthesized samples.The electrical conduction of the samples accords with a small-polaron hopping mechanism based on the facts that the temperature dependence of the conductivity is linear and the activation energies of the samples are low (E_a= 0.07584 eV, 0.07798 eV)in the range of 25～500 ℃. Ca~(2+) and Fe~(3+) doping is an effective method to improve the compatibility of thermal expansion with electrolytes. The reason was analyzed.