Abstract: An electrolyte sheet comprises a substantially non-porous body and has at least one stress-relief area on at least a portion of the electrolyte sheet. The stress-relief area has a surface with a plurality of folds. The plurality of folds are arranged around and directed longitudinally toward a common central area.

Abstract: A stress reducing mounting for an electrolyte sheet assembly in a solid electrolyte fuel cell is provided that includes a support frame or manifold having an inner edge portion that supports a peripheral portion of the sheet assembly, a seal that affixes an edge of the peripheral portion to the frame or manifold, and a stress reducer disposed around the peripheral portion of the electrolyte sheet and the frame or manifold that reduces tensile stress in the peripheral portion of the electrolyte sheet when the peripheral portion is bent by pressure differentials or thermal differential expansion. The stress reducer is at least one of a convex curved surface on the inner edge portion of the frame or manifold that makes area contact with the peripheral portion when it bends in response to a pressure differential or thermal differential expansion, and a stiffening structure on the sheet peripheral portion that renders the ceramic sheet material forming the peripheral portion more resistant to bending.