Phase and microstructure development of LSCM perovskite materials for SOFC anodes prepared by the carbonate-coprecipitation method

Abstract

Most SOFC development has been based on nickel yttria-stabilized zirconia anodes. Such materials have excellent catalytic properties for fuel oxidation, high electrical conductivity, good mechanical strength and an appropriate thermal expansion coefficient compatible with other cell components. Unfortunately, cermet anodes based on doped zirconia exhibit some disadvantages, e.g., the catalysing side reaction of carbon deposition during hydro-carbon fuel oxidation and a susceptibility to sulphur poisoning. Perovskite-type compounds based on lanthanum-strontium-manganese-chromium oxide (LSCM) can serve as an alternative material. Since the optimal perovskite composition is still not known, La1-xSrxMnyCr1.yO3±d (x from 0 to 0.3 and y from 0.4 to 0.6) ceramics were prepared with the co-precipitation method. Crystalline phase formation was followed by X-ray powder diffraction and Rietveld refinement. Quantitative microstructure analysis of the samples sintered at various temperatures was performed on SEM micrographs using Axiovision 4.8 software. Keywords: co-precipitation, oxide LSCM anode, phase development, microstructure Ve~ina razvoja visokotemperaturnih gorivnih celic je temeljila na anodnih materialih na osnovi niklja in cirkonijevega dioksida, stabiliziranega z itrijem. Ta ima odli~ne katalitske lastnosti pri reakciji oksidacije goriva, visoko elektri~no prevodnost, dobro mehansko trdnost in temperaturni razteznostni koeficient, skladen z ostalimi komponentami celice. @al so ti materiali med delovanjem podvr`eni ne`elenim reakcijam izlo~anja ogljika in zastrupljanja z`veplom, zato jih posku{amo nadomestiti z oksidnimi spojinami perovskitnega tipa, z lantan-stroncij-mangan-krom oksidom (LSCM). Optimalna sestava teh materialov {e ni znana, zato smo z metodo soobarjanja pripravili keramiko La1-xSrxMnyCr1.yO3± d (x od 0 do 0,3 in y od 0,4 do 0,6). Z rentgensko pra{kovno analizo in Rietveldovim prilagajanjem smo spremljali razvoj kristalnih faz. Z analizo SEM posnetkov vzorcev po sintranju pri razli~nih temperaturah smo mikrostrukture pripravljenih materialov kvantitativno ovrednotili z uporabo programa Axiovision 4.8.

Novel materials based on La0.75SrxA0.25-xCr0.5Mn0.5O3 (A=Ba, Ca, Mg) as full-ceramics anodes in high-temperature fuel cells

“…According to the phase diagram, the SrO-Cr 2 O 3 secondary phase SrCrO 4 forms a liquid phase due to eutectic and peritectic reactions that promote sintering, but only by adding Sr to perovskite under certain concentration x = 0.20. 19,30 The Sr 2 CrO 4 -rich phase presence in the as prepared materials was confirmed in samples with higher Sr content (x = 0.15, 0.20 and 0.25), which at higher temperatures first turns to SrCrO 4 and later forms a liquid phase to promote perovskite sintering. 20 With noticeable grain growth, the slightly decreased shape factor Y indicates that grains become diverse to ideal spheres, as already observed in the case of combustion-derived LSCM ceramics.…”