A composite oxygen ion transport membrane (1) having a dense layer (10), a porous support layer (12), an optional intermediate porous layer (14) located between the porous support layer (12) and the dense layer (10) and an optional surface exchange layer (16), overlying the dense layer (10). The dense layer (10) has electronic and ionic phases. The ionic phase is composed of scandia doped, yttrium or cerium stabilized zirconia. The electronic phase is composed of a metallic oxide containing lanthanum, strontium, chromium, manganese and vanadium and optionally cerium. The porous support layer (12) is composed of zirconia partially stabilized with yttrium, scandium, aluminum or cerium or mixtures thereof. The intermediate porous layer (14), if used, contains the same ionic and electronic phases as the dense layer. The surface exchange layer (16) is formed of an electronic phase of a metallic oxide of lanthanum and strontium that also contains either manganese or iron and an ionic phase of scandia doped zirconia stabilized with yttrium or cerium.