Formation, sintering and thermal expansion behaviour of Sr- and Mg-doped LaCrO3 as SOFC interconnector prepared by the ethylene glycol polymerized complex solution synthesis method

Sr- and Mg-doped LaCrO3 nanosized powders were succesfully synthesized from a polymeric precursor solution containing the respective aqueous solution of metal nitrate, chromium (111) nitrate, nitric acid, and ethylene glycol. The presence of a chromate solid solution of the type La-0.8 Sr-0.2 Cr1-xMgx O-4 (xless than or equal to0.2) as a low-temperature intermediate to perovskite-type is experimentally established using TG/DTA and XRD. In Sr, Mg-substituted LaCrO3, single-phase perovskite La0.8Sr0.2Cr1-xMgx O-3 was formed at about 770 degreesC by decomposition of the chromate phase solid solution, which crystallizes at about 520 degreesC from amorphous powders. La0.8Sr0.2Cr1-x Mg-x O-3 perovskite solid solution powders with surface areas as high as 11 m(2)/g and nanosized particles sintered at 1550 degreesC for 6 h in air were higher than 97% dense materials. Such an improvement in densification can be attributed to a two-stage shrinkage process, i.e., liquid phase formation and solid perovskite particle rearrangement in the liquid, respectively. No significant variations in both the final density and grain size with increasing Mg content were detected. Compositions La-0.8 Sr-0.2 Cr-0.9 Mg-0.1 O-3 and La-0.8 Sr-0.2 Cr-0.85 Mg-0.15 O-3 here investigated were shown to have negligible thermal expansion mismatch with YSZ electrolytes. The mixed oxide route was also used for comparison. (C) 2003 Elsevier Ltd. All rights reserved.