The Applicability of Sr-deficient n-type SrTiO3 for SOFC Anodes

Here we discuss the effect of preparation conditions on structural stability and electrical properties of Sr-deficient n-type SrTiO3. In particular, an explanation of a wide scatter of conductivity values in Y- and Nb-doped SrTiO3. reported in the literature is proposed, based on the existing defect chemistry model of n-doped SrTiO3. It was confirmed that when sintered in air, Sr-deficient SrTiO3 doped with Nb and/or Y, remains single phase until the solubility limit (e.g., 30% for Nb or 4% for Y). However, when sintered at low po2, the material transforms from a vacancy compensated to an electronically compensated compound with a strontium deficient second phase. Measured at 800°C in low po2, the maximum conductivity of these multi-phase compounds was 340 S/cm and 100 S/cm for the Nb-doped and Y-doped sample, respectively. However, the conductivity dropped dramatically to less than 10 S/cm when samples of the same compositions were sintered in air, again measured in reducing atmosphere.