反向滴定共沉淀法合成新型中温固体氧化物燃料电池阴极材料La_(0.7)Sr_(0.3-x)Ca_xCo_(1-y)Fe_yO_(3-δ)

SYNTHESIS OF NEWCATHODE MATERIALS La_(0.7)Sr_(0.3-x)Ca_xCo_(1-y)Fe_yO_(3-δ) BY REVERSE-TITRATION CO-PRECIPITATION METHOD FOR ITSOFC

以氢氧化钠和碳酸钠混合碱为沉淀剂,金属硝酸盐为原料,共沉淀法合成了中温固体氧化物燃料电池阴极材料La0.7Sr0.3-xCaxCo1-yFeyO3-δ(简称:LSCCF,x=0.05、0.10、0.15、0.20;y=0.10、0.20、0.40)的前躯体。讨论了共沉淀的最佳pH值范围以及加料顺序,TG-DSC研究了LSCCF粉料的形成过程,XRD和SEM对其前驱体在600℃,800℃,1000℃煅烧4h后的晶体结构和粒度形貌进行了研究和表征;并通过与固相合成LSCCF的条件比较可知:pH值在9.1～9.5范围内,反向滴定共沉淀法得到的前驱体在800℃煅烧4h可以合成出纯度高、组份均匀的单一钙钛矿相的LSCCF粉料。使用直流四极探针法在空气气氛下研究不同烧结温度下LSCCF样品从100℃到800℃时的电导率发现:电导率随着烧结温度的升高在增大;随着x从0.05到0.20以及y从0.10到0.40,1200℃烧结3h后样品的电导率却在减少;当x=0.10或0.15时,Ca2+和Sr2+掺杂对电导率产生"混合"效应,致使其值基本相等。且在500～800℃范围所有样品的电导率都超过了100S/cm。合成的阴极材料LSCCF与电解质Ce0.8Sm0.2O2两者间有良好的相容性。

The precursors of La0.7Sr0.3-xCaxCo1-yFeyO3-δ （LSCCF, x=0.05, 0.10, 0.15, 0.20; y=0.10, 0.20, 0.40） as the cathode materials for intermediate temperature solid oxide fuel cell were prepared by reverse-titration coprecipitation method with metal-nitrates as starting materials and mixed alkali （NaOH and Na2CO3） as a precipitating agent. The formation process of LSCCF from the precursors was monitored by TG-DSC, the crystal structure and particle morphology of the precursors which were calcined at 600℃, 800℃ and 1000℃ for 4h were characterized using XRD and SEM technologies. Compared with the solid state reaction of constituent oxides, when the PH value of the precipitating solution is in the range of 9.1 -9.5, the LSCCF powders calicned at 800℃ for 4h have high purity, homogeneous and single perovskite phase. The electrical conductivity of different sintered samples of LSCCF was measured as a function of temperatures from 100℃; to 800℃ by DC four-probe method in air. The conductivity increases with the sintedng temperature and the conductivity of samples sintered at 1200℃ for 3h decreases with x from 0.05 to 0.20 and y from 0.10 to 0.40. While x=0.10 or 0.15, the value of electrical conductivity is almost equal because of Ca^2＋, Sr^2＋ co-doping resulting in the ＂mixed effect＂. The electrical conductivity of all doped samples is higher than 100 S/cm at intermediate temperatures from 500℃ to 800℃, and there is good compatibility between LSCCF cathode and Ce0.8Sm0.2O2 electrolyte.