The La0.7Sr0.3CryMnzCo(1-y-z)O3-δ samples were prepared by solid state reaction.The phases,microstructure and properties of the samples were investigated by XRD,SEM,DC four-probe method and iodometry method.The single orthorhombic phase La0.7Sr0.3CryMnzCo(1-y-z)O3-δ perovskite oxides were obtained when sintered at l350 °C for 10 h.The oxygen nonstoichiometry of the materials varied inversely with the total electronic conductivity.The sample with composition of La0.7Sr0.3Cr0.5Mn0.35 Co0.15O3-δ had the maximal total electronic conductivity and the lowest oxygen nonstoichiometry which were 22.4 S/cm and 0.040 at 850 °C,respectively.The low total electronic conductivity is related to the low relatively density of the samples directly.The activation energy of conduction changed at 550 °C,and the activation energy of conduction at high temperature(T>550 °C) was higher than that at low temperature range(T<550 °C).
La0.7Sr0.3Cr0.5Mn0.4Co0.1O3±δ anode material was synthesized by glycine nitrate process. X-ray diffraction patterns indicate that single perovskite phase was created after sintering the predecessor at 1623 K for 5 h. By means of four-probe direct current, the electrical conductivities of La0.7Sr0.3Cr0.5Mn0.4Co0.1O3±δ were tested in different atmospheres, the maximum values were 10.2 S·cm-1 in air, 4.5 S·cm-1 in CH4 and 0.42 S·cm-1 in H2 at 1073 K, respectively. The compatibility between La0.7Sr0.3Cr0.5Mn0.4Co0.1O3±δ and La0.9Sr0.1Ga0.8Mg0.2O3-δ were investigated via X-ray diffraction and scanning electron microscopy, which shows that La0.7Sr0.3Cr0.5Mn0.4Co0.1O3±δ oxide, has good chemical and thermal compatibility with La0.9Sr0.1Ga0.8Mg0.2O3-δ. An electrolyte supported single cell consisted of La0.7Sr0.3Cr0.5Mn0.4Co0.1O3±δ|La0.9Sr0.1Ga0.8Mg0.2O3-δ|La0.9Sr0.1Ca0.1Fe0.8Co0.2O3±δ was fabricated through screen printing method. The open circuit voltage of the cell is about 0.92 V, and the maximum power density is about 75 mW·cm-2 at 1123 K.
La0.8Sr0.2Co1-yFeyO3-δ (y=0.2, 0.4, 0.6, 0.8) powders were synthesized by ethylenediamine tetraacetic acid (EDTA) complexing sol-gel process. The powders were characterized via X-ray diffraction (XRD) and scanning electron microscope and energy dispersive X-ray spectroscopy (SEM-EDS). The results showed that single-phased perovskite-type oxide powders with small particle size were obtained by the process, and the compositions of the productions agreed with the designed molar ratio. The electronic conductivity and ionic conductivity of La0.8Sr0.2Co1-yFeyO3-δ were investigated by DC four-terminal method and AC impedance spectroscopy, respectively. The electronic conductivity of La0.8Sr0.2Co1-yFeyO3-δ is approximately 2～4 orders of magnitude higher than the ionic conductivity. It was confirmed that the conductivities of the materials were strongly influenced by the composition anions, temperature and sample preparing process.
It was prepared by glycine-nitrate process (GNP) method for a novel composite material La0.7Sr0.3Cr0.5Mn0.5O3-δ-Ce0.8Ca0.2O2-δ (LSCM-CDC) used for anode of intermediate temperature solid oxide fuel cell (ITSOFC). The microstructure and properties of composite anode LSCM-CDC were measured via X-ray diffraction (XRD), scanning electron microscopy (SEM), AC impedance and four-probe direct current methods. Fluorite-perovskite compounded phase structure was obtained after being sintered at 1400 ℃ for 15 h, the optimum composition of the composite anode of LSCM and CDC was 7 to 3 at molar ratio. At 850 ℃, the electronic conductivity was 6.49 S·cm-1 in air and 1 S·cm-1 in the reduction atmosphere, respectively. The AC impedance spectra with two arcs showed that LSCM-CDC had low ionic conductivity, which was about two orders of magnitude lower than the electronic conductivity. LSCM-CDC composite anode was stable under different temperatures in pure methane gas with good catalytic performance, which indicated that the composite was a promising anode for ITSOFC.
