Conductivity Reaserch of Sr-deficient LSCF Perovskite Structure Synthesis by Glycine-Nitrate Process

• Main Authors: Hao-Yu Chien, 簡浩宇
• Other Authors: 余炳盛
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/28396k

碩士 === 國立臺北科技大學 === 資源工程研究所 === 98 === In this study, nanocrystalline perovskite structured La0.6Sr(0.4-x)Co0.2Fe0.8O3-δ powder with A-site-deficiency and an average particle size of 50~150mm was prepared by glycine-nitrate process to improve the sintered behavior and serve as the cathode material of IT-SOFC(intermediate temperature - solid oxide fuel cell). Rietveld structure refinement was adopted to perform X-Ray diffraction data analysis for providing models to explain the relationship between conductivity and structure. Iodometric titration and thermogravimetic analysis were used to calculate the oxygen nonstoichiometry. Findings indicated that greater Sr-deficiency led to higher deficiency of oxygen ion. However, the oxygen deficiency was restricted by lattice distorted in the temperature range of 400 to 800ºC.Oxygen deficiency below 400 ºC could be improved by sufficient Sr-deficiency to help increase electric conductivity. The composition of La0.6Sr0.35Co0.2Fe0.8O3-δ reported the highest conductivity of 453S/cm at 700 ºC after sintered at 1300 ºC for 2 hour. Though the composition of La0.6Sr0.4Co0.2Fe0.8O3-δ provided greater oxygen deficiency at temperatures above 400ºC, the contribution of the small polar hopping mechanism to conductivity was reduced. Rietveld refinement results indicated all the adjustment criteria lower than 9%, show all the models have sufficient accuracy. According the refinement results , the conductivity behavior could distingush to several parts：below 350℃,the conductivity was improved by the oxygen deficiency increasement although it was restricted by lattice constant at 550℃. The higher temperature induced the lattice to tolerate more oxygen deficiency but declination of conductivity, even when the temperature upon 700℃ compensation of semi-conductor-like mechanism became insufficient, then the electric conductivity decline.