Glass seal containing zirconia powder and fiber for a solid oxide fuel cell stack

A glass ceramic composition for sealing adjacent metal cassettes in an SOFC stack. The seal composition comprises an alumina-silicate glass ceramic matrix or a matrix of Zr2 and a ceramic fiber aggregate and non-fibrous zirconia dispersed in the matrix. Preferably, the fiber is selected from the group consisting of zirconium oxide fiber, alumina fiber, and combinations thereof. Preferably, the fiber is present at 1-60 weight percent with respect to the weight of glass ceramic, preferably about 30 weight percent. Preferably, the zirconia fiber is stabilized by up to about 10% yttria. Alumina fiber may substitute for a portion of the zirconia fiber. Preferably, the non-fibrous zirconia is present at about 5 weight percent and is also stabilized.