REACTIONS AT THE CALCIUM-DOPED LANTHANUM CHROMITE-YTTRIA STABILIZED ZIRCONIA INTERFACE

Solid oxide fuel cell materials calcium doped lanthanum chromite (La,C a)CrO3 and yttria stabilized zirconia (YSZ) are known to interact with each other, This interaction causes interruption of cosintering proce sses and the formation of secondary phases which degrade fuel cell per formance. The present study shows by X-ray diffraction and microscopic analysis that Ca migrates via an exsolved Ca-Cr-O liquid phase emanat ing from (La,Ca)CrO3 and reacts with YSZ to obtain an intermediate lay er of CaZrO3, The width of the CaZrO3 reaction region was found to inc rease with increasing Ca content in the exsolved Ca-Cr-O second phase. Calcium zirconate was observed to react with YSZ along the YSZ grain boundaries, eventually digesting YSZ grains into a CaZrO3 matrix. The results demonstrate the improbability of cosintering (La,Ca)CrO3 and Y SZ in the presence of the Ca-Cr-O liquid phase and illustrate the impo rtance of obtaining single phase (La,Ca)CrO3 to achieve compatibility with YSZ. (C) 1996 Academic Press, Inc.