Improved electrical performance and sintering ability of the composite interconnect La_0.7Ca_0.3CrO_3-δ/Ce_0.8Nd_0.2O_1.9 for solid oxide fuel cells

Significant improvements on sintering characteristic and electrical performance of traditional interconnect La_0.7Ca_0.3CrO_3-δ were presented in this paper. For a composite interconnecting ceramic La_0.7Ca_0.3CrO_3-δ/Ce_0.8Nd_0.2O_1.9, it was found that the addition of Ce_0.8Nd_0.2O_1.9 significantly increased the electrical conductivity of La_0.7Ca_0.3CrO_3-δ both in air and in hydrogen. Among all the investigated specimens, La_0.7Ca_0.3CrO_3-δ with 5 wt% Ce_0.8Nd_0.2O_1.9 possessed the maximal electrical conductivity. In air and hydrogen, the maximal electrical conductivity at 800 °C were 55.4 S cm^-1 and 5.0 S cm^-1, respectively, which increased significantly as compared with La_0.7Ca_0.3CrO_3-δ under the same conditions. With the increase of Ce_0.8Nd_0.2O_1.9 content the relative density increased, reaching 97.1% from 93.9% of La_0.7Ca_0.3CrO_3-δ. This indicated that Ce_0.8Nd_0.2O_1.9 functioned as an effective sintering aid in enhancing the sinterability of the powders. The average coefficient of thermal expansion at 30-1000 °C in air increased with Ce_0.8Nd_0.2O_1.9 content. Most coefficients of thermal expansion of specimens are compatible with other cell components. The oxygen permeation measurement illustrated a negligible oxygen ionic conduction, indicating it is still an electronically conducting ceramic. Results indicate that this composite is suitable to be used as a high-performance interconnect for intermediate temperature solid oxide fuel cells.