Boosting room-temperature thermoelectricity in SrTiO3-based superlattices†

Despite the breakthrough of heavy-metal-based thermoelectric materials, achieving high performance for environmentally friendly oxide-based thermoelectric materials is still a big challenge. In this work, we introduced tensile strain into the [(SrTiO₃)_m/(SrTi_0.8Nb_0.2O₃)_n]_t superlattices using DyScO₃(110) substrates for epitaxial growth. The tensile strain effectively increased the ferroelectric transition temperature (T_C) of the SrTiO₃ superlattices from 105 K to 250 K. The phonon scattering due to the ferroelectric domain wall and soft phonon mode cumulatively lowered the thermal conductivity, boosting the dimensionless figure of merit (ZT) to 1.2 and power factor (PF) to 10.5 mW m⁻¹ K⁻² at 300 K. These results suggest that tuning epitaxial strain is highly effective in enhancing thermoelectricity when combined with phonon-glass electron-crystal strategy, paving a new route for designing high-performance oxide-based thermoelectric materials.