Ionic conductivity, structural and thermal properties of pure and Sr ²⁺ doped Y₂Ti₂O₇ pyrochlores for SOFC

In the present study, SrO doped Yttrium titanate pyrochlore was synthesized using solid state reaction technique. The sintering characteristics, crystal structure, thermal and conductivity behavior of doped and undoped pyrochlores have been studied to find their suitability in solid oxide fuel cells (SOFC). The as-prepared samples were characterized using X-ray diffraction (XRD), Fourier-Transform-Infrared spectroscopy (FT-IR), thermal-gravimetric analysis (TGA) and ac conductivity up to 900 °C. The results are discussed in light of oxygen vacancy formation and structural disordering. Undoped and doped yttrium titanate with SrO (x = 0.1) exhibits single Y₂Ti ₂O₇ phase with relative density of 94%. It was observed that further doping of SrO (x = 0.2-0.4) leads to formation of Y ₂Ti₂O₇ phase along with SrTiO₃ phase. Excessive SrO (x = 0.4) results in increase in ionic conductivity to 1.50 × 10^-1 S cm^-1 whereas it impedes the densification process with relative density of 85%.