LaSrMn and YSZ Tape Casted Materials for SOFCs Characterized by X-ray Diffraction and EBSD

R. E. BOLMARO; J. ESCOBAR; M. AVALOS; R. JANSSEN; H.-G. BROKMEIER; M.T. COLOMER; R. MORENO

Joinville

Congreso; Congresso Brasileiro de Engenharia e Ciência dos Materiais; 2012

CBECIMAT

Commercial submicron size powders of strontium-doped lanthanum manganite (La0.85 Sr0.15)0.98MnO3 (LSM85, Inframat Advanced Materials, USA) and cubic ZrO2 stabilized with 8 mol% Y2O3 (8YSZ, TOSOH, Japan) were used as starting materials. The average particle size (laser diffraction, Mastersizer S, Malvern, UK) was 0.25 µm for LSM and 0.4 µm for 8YSZ, respectively. The specific surface area (single-point BET method, MonosorbTM Surface Area Analyzer MS-13, Quantachrome Corporation, USA) was 2.8 m2/g for LSM and 4.7 m2 g-1 for 8YSZ, respectively, the density (Multipicnometer, Quantachrome Corporation, USA) was 6.30 g/cm3 for LSM and and 6.0 g/cm3 for 8YSZ, respectively. Suspensions were prepared in water to a solids loading of 55 vol.% with an ultrasound (US) probe (UP 400S, Dr Hielscher GmbH, Germany) in order to prevent agglomeration for 1 min. A commercial polyacrylic acid-based polyelectrolyte - PAA (DURAMAXTM D-3005, Rohm & Haas, USA) was used as a deflocculant with additions of 0.5 wt% (on a dry solids basis). Tape casting slips were prepared adding 10 wt% of an acrylic emulsion (Duramax B-1000, Rohm & Haas, USA) binder, which has an active matter content of 55 wt%. The different suspensions were cast in a self-made tape casting machine with moving deposit at a casting speed of 5 cm/s and blades height of 200 and 100 µm. LSM green tapes were sintered in air by firstly heat treat at 500ºC for 30 min, to burn out the organic matter, and then treated at 1500ºC for 2 h or 4 h with heating and cooling rates of 5ºC min-1. Green sandwiches of LSM/8YSZ were also prepared by tape casting.  Resultant materials were characterized by laboratory X-ray diffraction and synchrotron radiation. The laboratory diffractometer was a Panalytical MPD equipped with Cu tube, x-ray lens, graphite monochromator and parallel plate collimator in a parallel beam array. Synchrotron radiation from LNLS Brazilian synchrotron and Petra III – HEMS beams were 1.1268 Å and 0.241 Å respectively. Previous Si and LB6 standards were used to characterize machine broadening and later on Rietveld analysis as implemented in MAUD software was used to characterize composition, grain size and residual strains. Further characterization was performed by EBSD. Samples of both were included in conductive resin and polished with diminishing grit sand paper and later on with 9, 6, 3 and 1 micron diamond water solutions. Polished samples were characterized in a FEI-FESEM Quanta 200 microscope equipped with EDS EDAX and Electron Back Scattering Diffraction  (OIM-TSL). The analysis allowed the determination of local crystallographic orientation (micro-texture), grain size distribution, defect content (porous volume fraction included) and local misorientations. The results will be discussed and correlated with x-ray results.