Lanthanum strontium manganite (LSM) can be thermal expansion-matched with undoped ceria (CeO2) or Gd2O3-doped ceria (CGO) by incorporating equimolar amounts of the A-site cations La and Sr. Such high Sr levels, however, can result in low elastic modulus and room-temperature plastic deformation, as well as low strength that would be typical of a microcracked ceramic. The addition of a continuous ceria network to such LSM compositions allows the composite material to behave mechanically like ceria, while still maintaining substantial electrical conductivity. The LSM and ceria in these composites show minimal reactivity after sintering, regardless of whether the ceria is doped or undoped. In addition, there is little penalty for sintering the composites relative to the monolithic materials. The composite materials are two to three times stronger than LSM, with the plastic deformation decreasing as the strength increases. Conductivity considerations are discussed for both mixed ionic-electronic conducting (MIEC) devices and interconnects for oxygen generation. (C) 2003 Elsevier Science B.V. All rights reserved.