Synthesis, crystal stability, and electrical behaviors of La0.7Sr0.3Cr0.4Mn0.6O3−δ–XCu0.75Ni0.25 for its possible application as SOFC anode

• Published in: Journal of materials science 2012-12, Vol.47 (23), p.8118-8127
• Main Authors: Alvarado-Flores, J., Bocanegra-Bernal, M. H., Espitia-Cabrera, I., Torres-Moye, E., Reyes-Rojas, A.
• Format: Article
• Language: English
• Subjects: Anodes; Characterization and Evaluation of Materials; Chemical precipitation; Chemistry and Materials Science; Classical Mechanics; Copper; Crystal structure; Crystallography and Scattering Methods; Crystals; Dependence; Electrical resistivity; Grain growth; Materials Science; Nanocomposites; Nanoparticles; Nickel; Perovskites; Polymer Sciences; Porosity; Reaction mechanisms; Rietveld method; Sintering (powder metallurgy); Sol-gel processes; Solid Mechanics; Solid solutions; Sublimation; Symmetry; Thermal expansion
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-012-6707-5

La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3−δ (perovskite-type) nanocomposites impregnated with X Cu 0.75 Ni 0.25 have been synthesized by sol–gel method. Crystal structure of LSCM–Cu 0.75 Ni 0.25 composites were refined by the Rietveld method. Crystal symmetry of CuO and NiO nanoparticles have monoclinic and cubic symmetry, respectively, but after sintering at 1,200 °C and reducing the temperature to 600 °C, it’s transformed into a new Cu 0.75 Ni 0.25 intermetallic solid solution without secondary phase. We have detected a cationic inter-diffusion in Cu ↔ Ni interphase crystals during this reduction process; however, when sintering time exceeds 2 h at 1,200 °C this reaction mechanism is interrupted by a sublimation phenomenon; which causes Cu 2 O cubic structure segregation from monoclinic CuO structure. This leads to Cu precipitation from the Cu 1− x Ni x solid solution. Cu 0.75 Ni 0.25 inhibits the LSCM perovskite-type grain growth ( t  ≈ 220 nm). Electrical conductivity indicates the presence of semiconductor and metallic-type behaviors with a maximum electrical conductivity (800 °C) >4.5 (log σ, Sm cm −1 ). When Cu 0.75 Ni 0.25 concentration was 25 and 35 %, semiconductor behavior were dominated. Thermal expansion coefficients showed a linear dependence inversely proportional to Cu 0.75 Ni 0.25 concentration. Electrical conductivity, Rietveld analysis, Porosity, TEC, and E a behaviors lead to the conclusion that the anodes between 25 and 35 % (Cu 0.75 Ni 0.25 ) are closer to applications at SOFC.