Electrical properties of yttrium-doped strontium titanate under reducing conditions

The electrical conductivity of SrTiO3 containing rare earth dopants (Y, La, Pr, Sm, Nd, Gd, or Yb) was measured at 600-900 degreesC in reducing atmospheres. An unusually high conductivity was observed for the yttrium-doped samples compared to those with rare earth dopants, particularly at the composition of the solubility limit Sr0.88Y0.08TiO3-delta where the conductivity at 800 degreesC was 64 S/cm. The conductivity was confirmed to be n-type by thermopower measurements. The oxygen deficiency was determined to be 1% by thermogravimetric analysis. Increasing the strontium vacancy concentration to Sr0.86Y0.08TiO3-delta effected a further improvement in conductivity to 82 S/cm. This material has high structural stability over a broad range of temperature (up to 1400 degreesC) and oxygen partial pressure (1-10(-20) atm). A simple defect model was developed to explain the change of electrical conductivity as a function of yttrium content and oxygen deficiency. (C) 2001 The Electrochemical Society.