Preparation And Study On The Property Of LaSr₃Fe_3-xMn_xO_10-δ And LaSr₃Fe₃O₁₀-Ce_0.8Sm_0.2O₂ Mixed Conductor

The perovskite structure of oxides have a wide range of technical application in catalysis, SOFC and oxygen sensor et al.The structures, electrical property, oxygen diffusion mechanism and the cathode electrochemical performance of La Sr3Fe3-xMnxO10-δ mixed conductor and La Sr3Fe3O10-Ce0.8Sm0.2O2 dual phase materials were studied in this paper.La Sr3Fe3-xMnxO10-δ(x=0.0-0.8) mixed conductors with layered perovskite structure were prepared via citric acid method. XRD analysis showed that the cell volume decreased with Mn content. The fraction of Fe4+ concentration to the concentration of tetravalent ions decreased with the increase of Mn content. The decrease of VB of La Sr3Fe3-xMnxO10-δ samples with the increase of temperature gave rise to the drop of p type charge carriers and the increase of oxygen vacancies. The formula of the relationship between VB and the numbers of the configurations of transition metals in La Sr3Fe3-xMnxO10-δ was deduced and hence the possible filling states of 3d orbitals of Fe and Mn ions at 700℃ and 800℃ were given. Scanning Kelvin probe measurement results revealed that the surface potential of x=0.6 sample was the highest while x=0.8 sample was the lowest. The higher the surface potential, the higher the energy needed for an electron to be released from the sample. The coefficient of oxygen diffuse was measured by method of electrical conductivity relaxation. The oxygen diffusion coefficients increase with the temperature while decrease with the manganese content(x ≤ 0.4 range).The apparent activation energy Ea decreased with the Mn-doped quantity.The dual phase specimen of La Sr3Fe3O10-Ce0.8Sm0.2O2 were perpared by means of solid state reaction.By using four-terminal method, the La Sr3Fe3O10-Ce0.8Sm0.2O2 dual phase specimen conductivity were studied. The maximum conductivity of LSFO-SDC dual phase specimen offset to the high temperature with the increased SDC-doped quantity.Among that, the conductivity properties of LSFO-SDC=2:8 was close to pure SDC. The scaning Kelvin probe was used to test the superficial potential of LSFO-SDC dual phase specimen with different SDC-doped quantity. Qualitative analysised of sample surface electron was stimulated energy required.Using brushing method to preparation four volume ration of cathode half cell. The electrochemical properties of SDC-doped half cells were studied by means of impedance spectrum. The results showed that the solution of oxygen adsorption capacity enhanced, the chemical reaction rate was accelerated and the oxygen ion mobility accelerated as the temperature increases,so promoting the reduction of oxygen and oxygen ion transfer, enhancing the catalytic activity for oxygen cathode, reducing the interface resistance. The impedance decrease with the increase of SDC-doped quantity.According to the Tafel graph, with the increase of SDC content, the Tafel coefficient decreased, accelerate the speed of electrode reaction.