Simultaneous realization of high power factor and low thermal conductivity in medium-entropy La-doped (Sr_1/3Ba_1/3Ca_1/3)_1-xLa_xTiO₃ oxides with porous structure

Some studies have proven the effectiveness of high-entropy alloying in reducing lattice thermal conductivity; however, the synchronous degradation in carrier mobility limits the thermoelectric properties of high-entropy materials. Herein, we present a series of medium-entropy oxides (Sr_1/3Ba_1/3Ca_1/3)_1-xLa_xTiO₃ (x = 0.05, 0.1, 0.15) with different levels of La doping, breaking the trade-off between carrier and phonon transport. The medium-entropy design helps keep the carrier mobility at a moderate level while modulating the carrier concentration through La³⁺ doping, thereby yielding a peak power factor value of 1842 μW/(m⋅K²) at 773 K. Meanwhile, the incorporation of nano-micro-porous structure and medium entropy effect leads to a significant reduction in lattice thermal conductivity, reaching 2.3 W/(m⋅K) at 1073 K. Consequently, a ZT_max value of 0.67 is obtained for the MEP-10La sample at 1073 K, which is one of the state-of-the-art ZT values reported for the SrTiO₃-based materials. The present work provides a viable approach for the development of thermoelectric materials with enhanced performance.