CO_2气氛中La掺杂BaCo_(0.88)Nb_(0.12)O_(3-δ)膜的透氧性能及结构稳定性

Oxygen Permeation Property and Structural Stabiltiy of La-doped BaCo_(0.88)Nb_(0.12)O_(3-δ) Membranes in CO_2 Atmosphere

利用固相合成法制备了A位La掺杂Ba Co0.88Nb0.12O3-δ[BLCN-x,x为La的掺杂量(摩尔分数)]钙钛矿透氧膜材料,采用X射线衍射(XRD)、扫描电子显微镜(SEM)、热重分析(TG)及程序升温脱附-质谱(TPD-MS)等方法研究了CO2气氛静态处理及动态透氧条件BLCN-x系列材料的结构稳定性.研究结果表明,随着La掺杂量的增加,BLCN-x膜片材料抗CO2腐蚀的性能明显提高.当La含量高于0.5时,在850℃纯CO2气氛静态处理或透氧条件下均未观察到碳酸盐衍射峰.尽管La掺杂会降低BLCN-x膜片的初始透氧量,但在CO2气氛吹扫时透氧量的降低速率明显减慢,其中BLCN-0.5膜片在纯CO2气氛下10 h后的透氧量仍可达到0.46 m L·cm-2·min-1.通过容差因子和平均金属-氧键能计算可知,良好的结构稳定性和增强的金属-氧键能是导致La掺杂样品抗CO2腐蚀的主要因素.

La-doped BaCo0.88Nb0. 12O3-δ（ BLCN-x, x represents the molar ratio of La） perovskite membranes were prepared by solid phase reaction. The structrural stability of membranes was analyzed by X-ray diffraction （ XRD）, scanning electron microscopy（ SEM）, thermogravimetric （TG） analysis and temperature programmed desorption-mass spectrography（TPD-MS） methods. The results indicated that the CO2 tolerance properties of BLCN-x membranes were improved markedly with the increase of La content. Specially, the diffraction peaks of witherite can＇ t be observed for the membranes with a La content higher than 0. 5, whatever the membranes were calcined or conducted the oxygen permeation measurement with pure CO2 sweeping. The initial oxygen permeation flux of BLCN-x membranes would be reduced with the doping of La, however, the oxygen flux of BLCN-x membranes swept by CO2was more stable with the increase of La content. Particularly, the oxygen flux of BLCN-0. 5 membrane is about 0. 46 mL ·cm-2 ·min-1 after pure CO2 sweeping for 10 h. The better structural stability and CO2 tolerance properties of BLCN-x membranes with higher La content are due to more appropriate Goldschmidt tolerance factor and the enhanced average metal-oxygen bond energy.