Microstructure and enhanced seebeck coefficient of textured Sr₃Ti₂O₇ ceramics prepared by RTGG method

Textured Sr₃Ti₂O₇ ceramics (abbreviated as S3T) with grain orientation degree higher than 0.7 were successfully prepared by reactive-templated grain growth (RTGG) technique combined with tape casting process, using plate-like Sr₃Ti₂O₇ particles as templates. The phase transition, microstructure and thermoelectric properties were investigated. As the sintering temperature and soaking time increase, the density and texture fraction of ceramics increase. Textured Sr₃Ti₂O₇ ceramics were sintered in air and annealed in argon + graphene carbon (Ar+C) atmosphere. The results showed that the resistivity of textured Sr₃Ti₂O₇ ceramics annealed in Ar+C environment decreased significantly (seven orders of magnitude). After the annealing process, the texture fraction decreased, and Sr₃Ti₂O₇ phase on the surface of textured ceramics decomposed to SrTiO₃. The Seebeck coefficient was negative, and the absolute value of S increased with increasing temperature. Textured Sr₃Ti₂O₇ ceramics showed the maximum Seebeck coefficient (−399 μV/K) at 1073 K, which is higher than those of non-textured Sr₃Ti₂O₇-based materials.