Pore‐Defect Synergistic Decoupling of Electrical and Thermal Transport in Entropy‐Engineered Thermoelectric Ceramics

Pore engineering reduces the thermal conductivity of thermoelectric materials, yet typically degrades electrical conductivity by enhancing carrier scattering—a long‐standing trade‐off. Here, we overcome this trade‐off in SrTiO 3 ‐based entropy‐engineered ceramics via a one‐step synergistic strategy: using poly(methyl methacrylate) (PMMA) as a carbonaceous pore former, we simultaneously construct porous structures and in situ oxygen vacancies through pyrolysis under a reducing atmosphere. The oxygen vacancies compensate for the pore‐induced conductivity loss by elevating carrier concentration, whereas pores and defects jointly suppress lattice thermal conductivity. As a result, the lattice thermal conductivity decreases continuously, whereas the power factor is preserved, leading to a 20.41% enhancement in the thermoelectric figure of merit ( ZT ) compared to the dense counterpart. Model‐based estimation suggests that the pore contribution to thermal conductivity reduction grows steadily with porosity, whereas the estimated defect‐related contribution shows a tendency toward saturation. In contrast, pore‐only control samples (without additional PMMA‐induced oxygen‐vacancy enrichment) show a faster degradation of power factor than of thermal conductivity, yielding a ZT that is merely 56% of that achieved in the pore–defect synergistic sample, underscoring the necessity of defect compensation. This work establishes a feasible paradigm to decouple electrical and thermal transport in porous oxides, and provides atomic‐scale insights into the defect‐rich environment around pore walls.