Materials in the La(0.1)Sr(0.9)Co(1-y)MnyO(3-delta) (LSCM) family are potentially useful as ceramic membranes for high-temperature oxygen separations. A series of LSCM samples was synthesized by solid state methods and characterized by powder X-ray diffraction, thermogravimetric analysis, and four-probe conductivity. The materials were indexed in the cubic Pm-3m space group. TGA data implied that LSCM can reversibly absorb and desorb oxygen versus temperature and partial oxygen pressure, while powder diffraction data showed that the material maintained the cubic perovskite structure. Preliminary four-probe conductivity measurements signify p-type semiconducting behavior.(c) 2006 Elsevier B.V. All rights reserved.