Atomistic Investigation of the Second Phase Precipitation in (Sr,La)TiO_3 Interconnect Material

摘要

We investigated the second phase precipitation in (Sr,La)TiO_3 interconnect materials in SOFC by utilizing first-principles calculation. Our calculation showed that homologous phase La_2Ti_2O_7 is more stable than monoclinic pyrochlore phase by 0.59 eV/f.u. From the consideration of the precipitation mechanism and phase stability, Ruddlesden-popper phase and homologous phase are thought to precipitate within perovskite lattice under SOFC operation. Calculated band gaps of Ruddlesden-popper phase, pyrochlore phase and homologous phase were larger than that of pristine SrTiO_3. These intrinsic electronic state of precipitates should affect the electrical conductivity of (Sr,La)TiO_3 ceramics. Defect formation energy showed that La element and cation vacancy tend to segregate at grain boundaries, and work as sources of the precipitation.