Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)混合导体导电性能的研究

Electrical properties of mixed conductor Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)

用直流四电极法测量了空气和氮气气氛下Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF)的总电导率,用电子阻塞电极法测量了空气气氛下BSCF的氧离子电导率。结果表明575℃之前,BSCF呈现p型半导体的导电特征,总电导率温度升高而增大,随氧分压降低而减小;但在575～650℃总电导率显著下降,这与BSCF材料中晶格氧的逸出有关。通过电子阻塞电极法测得的BSCF氧离子电导率σi和温度T的关系符合Arrhe-nius公式,氧离子电导活化能Ea=140.7kJ/mol。通过透氧实验,由Wagner方程计算出来的氧离子电导率与电子阻塞电极法测量得到的值在700℃以下吻合;但700℃后,由于高氧端的气体与膜表面晶格氧的交换以及低氧端表面晶格氧与气相氧交换成为控速环节,使计算出来的氧离子电导率明显低于测量得到的值,并且二者差别随温度升高越来越大。

In this paper,the total conductivity of Ba0.5Sr0.5Co0.8Fe0.2O3-δ（BSCF） was investigated by the DC fourprobe measurement under the air and nitrogen atmospheres,the electronic blocking electrode measured ionic conductivity of BSCF under air atmosphere.The results showed that BSCF showed p-type semiconductor conductive characteristics,the total conductivity of BSCF increased with rising temperature and decreased with the decrease of oxygen partial pressure lower than 575℃;however,the total electrical conductivity dropped significantly due to escape of lattice oxygen of BSCF materia at 575-650℃.The relationship between temperature T and ionic conductivity σi measured by E-blocking electrode method is consistent with Arrhenius plot,and oxygen-ion conductance activation energy Ea=140.7kJ/mol.Oxygen ion conductivity calculated from Wagner formula is coincide with the value measured by electronic blocking method lower than 700℃;but oxygen ion conductivity is obviously lower than the value measured by electronic blocking method due to the exchange of gas and lattice oxygen of membrane surface of oxygen-rich side and the exchange of surface lattice oxygen and gas phase oxygen of hypoxia-side becoming the rate-limiting steps higher than 700℃,and the difference between them increased with rising temperature.