Conductivity of SrTiO3 based oxides in the reducing atmosphere at high temperature

The conductivities of several donor-doped SrTiO3 based oxides, which were prepared in air, were studied in a reducing atmosphere at high temperature. The conductivities of all specimens increased slowly with time at 1000 deg C in 9% H2/N2, even after 100h. Nb-doped SrTiO3 showed relatively fast reduction and high conductivity compared with the other SrTiO3 based oxides. The conductivity of Nb-doped SrTiO3 was ca. 50Scm-1 at 500 deg C after reduction at 1200 deg C. After strong reduction, the conductivity of Nb-doped SrTiO3 was almost independent of the oxygen partial pressure at 500-800 deg C, while that of La-doped SrTiO3 dropped immediately on exposure to air. The conduction behavior of Nb-doped SrTiO3 was explained by reduction of Ti4+ and/or Nb5+ and the relatively slow oxygen diffusibility.