The large thermal conductivity of SrTiO3 bulk material limits its potential application for high-temperature thermoelectricity. The effects of all-scale grain boundaries and inclusions on the thermoelectric performance of Nb-doped bulk SrTiO3 materials are investigated in this study. Nano- to microscale grain boundaries and inclusions reduce the thermal conductivity by 30%. As a result, the ZT value is enhanced 2.6 times by a combination of all-sized crystals, energy filtering effect, multilevel scattering behaviors of nano/microscale grain boundaries and inclusions.
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