Synergistic regulation of electron and phonon transport in SrTiO₃-based thermoelectric perovskites via entropy engineering of A-site cations

SrTiO₃-based thermoelectric oxides are promising candidates for high-temperature energy conversion because of their low cost, environmental compatibility, and excellent thermal stability. However, their relatively low thermoelectric performance remains a key limitation to practical applications. In this work, a series of multicomponent A-site medium- and high-entropy perovskite oxides, (Sr_1/2Ba_1/4Ca_1/4)_1-x(La_1/3Nd_1/3Sm_1/3)_xTiO₃ (SBC-RE_x; x = 0.08–0.18), were developed to simultaneously regulate electron and phonon transport. All samples maintain a cubic SrTiO₃ perovskite phase with Pm–3m symmetry and homogeneous elemental distribution. The doping of La³⁺, Nd³⁺ and Sm³⁺ electron donors modulates the electron carrier concentration, thereby increasing electrical conductivity while preserving moderate carrier mobility and effective mass, leading to enhanced power factor at x = 0.14. Meanwhile, entropy engineering via co-incorporation of multielement rare earth cations in the A-site induces chemical disorder, local lattice distortion and strain fields, which suppress grain growth and intensify phonon scattering, leading to reduced lattice thermal conductivity. Consequently, the optimized SBC-RE_0.14 sample achieves a power factor of 1.24 mW m⁻¹ K⁻² and thermal conductivity of 3.08 W m⁻¹ K⁻¹, reaching a maximum ZT of 0.31 at 773 K. This work demonstrates that A-site entropy engineering offers an effective strategy to balance electron and phonon transport in SrTiO₃-based oxide thermoelectrics.