Patent ID: 7955526

Claim:
A composite (M) comprising: a) at least 75 vol % of a mixed electronic/oxygen O 2− anionic conducting compound (C 1 ) which, at the use temperature, are in the form of a crystal lattice having oxide ion vacancies, compound (C 1 ) being a perovskite compound of a formula selected from the group consisting of: 1) La (1−x−u) Sr x Al u Fe (1−v)Ti v O 3−δ , 2) La (1−x−u) Sr x Al u Fe (1−v) Ga v O 3−δ , 3) La (1−x) Sr x Fe (1−v) Ti v O 3−δ , 4) La (1−x) Sr x Ti (1−v) Fe v O 3−δ , 5) La (1−x) Sr x Fe (1−v) Ga v O 3−δ or 6) La (1−x) Sr x FeO 3−δ where: 0<x≦0.5; 0≦u≦0.5; (x+u)≦0.5; 0≦y≦0.9; 0≦v≦0.9; 0≦(y+v)≦0.9; and w is such that the structure in question is electrically neutral; b) from at least 0.1 vol % but not more than 10 vol % of a compound (C 2 ) selected from the group consisting of magnesium oxide (MgO) and mixed barium titanium oxide (BaTiO 3 ); and c) from 0 vol % to 2.5 vol % of a compound (C 3 ) produced from at least one chemical reaction represented by the equation: x F C1 +y F C2 →z F C3 , in which equation F C1 , F C2 and F C3 represent the respective crude formulae of compounds (C 1 ), (C 2 ) and (C 3 ) and x, y and z represent rational numbers greater than or equal to 0.