La{sub}(2-x)Sr{sub}xNiO{sub}(4+δ) ceramic powders prepared by combustion synthesis

摘要

Combustion synthesis provides an attractive method of producing ceramic powders because of its low cost, process simplicity and fastness. Materials based on La{sub}2NiO{sub}(4+δ) can be successfully prepared by combustion synthesis. La{sub}(2-x)Sr{sub}xNiO{sub}(4+δ) (x = 0, 0.1) accommodates oxygen excess by oxygen interstitials rather than by the more usual cation vacancies. A high concentration of oxygen interstitials offers the possibility of rapid oxygen transport through the ceramic material and thus provide a new type of mixed ionic-electronic conductor. The fast oxide ion diffusion combined with its thermal stability indicate that these materials would be good candidates for use in Ceramic Oxygen Generators (COGs) and Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs). The present work discusses a combustion synthesis technique to prepare La{sub}(2-x)Sr{sub}xNiO{sub}(4+δ) (x = 0, 0.1) powders using the corresponding metal nitrates-urea mixtures, at low temperature and short reaction times. The as-prepared combustion powders were characterized by XRD, DTA-TG, SEM/TEM-EDX and BET. La{sub}(2-x)Sr{sub}xNiO{sub}4 (x = 0, 0.1) powders with a good compositional control and homogeneity are attained. The as-prepared powders obtained at 300°C (ignition temperature) showed much higher specific surface area than powders obtained via alternative routes and contained La{sub}(2-x)Sr{sub}xNiO{sub}(4+δ), as the major phase present, together with La{sub}2O{sub}3 and a small amount of Ni{sub}O. La{sub}(2-x)Sr{sub}xNiO{sub}(4+δ) single phase is achieved, respectively at 950°C for x =0.1 and at 975°C for x = 0.