We studied the influence of the magnetic phase transition on the transport properties of La0.7Ca0.3−xBaxMnO3 compounds with x = 0.05, 0.075, and 0.10. Our experimental results demonstrated the ferromagnetic-paramagnetic and metal-insulator transitions taking place at temperatures TC = 265–300 K and TMI = 280–310 K, respectively, which increase with increasing Ba-doping content. While the x = 0.05 sample undergoes a first-order magnetic phase transition (FOMT), x = 0.10 undergoes a second-order magnetic phase transition (SOMT). The other sample with x = 0.075 is considered as a threshold concentration of the FOMT-SOMT transformation. Further, ρ(T) data in different temperature regions were fitted to different models. The activation energy Ep and density of states at the Fermi level N(EF) were accordingly determined. Notably, N(EF) increases while Ep decreases in the case of applying an external field. We also have found that N(EF) increases when materials transfer from the FOMT to the SOMT, which becomes smallest for the sample having the coexistence of the FOMT and SOMT (i.e., x = 0.075).

Oxygen permeation fluxes through dense SrCo0.80Fe0.20O3-5 discs have been measured in the temperature range of 620-920 °C under various oxygen partial pressure gradients. The permeation results are compared with the previous measurements. Below 800 *C, the apparent activation energy for the overall permeation is 22±4 kcal/mol. The permeation results are discussed in light of the phase diagram of SrCo0.80Fe0.2003-8. Based on experiments in which the membrane thickness is varied, we propose that the surface exchange process is the ratelimiting step in the overall permeation reaction. Preliminary catalytic studies of methane partial oxidation in a membrane reactor are reported.