Microstructure and thermoelectric properties of non-equimolar high-entropy [Ca_(1-x)/3Sr_(1-x)/3Ba_(1-x)/3La_x]TiO₃ perovskite ceramics

Entropy engineering has emerged as an important means of optimizing the properties of SrTiO₃-based thermoelectric materials. However, the relationship between configurational entropy and thermoelectric properties is currently unclear. In this work, non-equimolar high-entropy thermoelectric ceramics [Ca_(1-x)/3Sr_(1-x)/3Ba_(1-x)/3La_x]TiO₃ (0.10 ≤ x ≤ 0.40) were prepared by spark plasma sintering. And the effects of composition and configurational entropy on the microstructure and thermoelectric properties of the materials were investigated. It is revealed that high entropy effect profoundly modified the microstructure of the material. The grain size decreases with increasing configurational entropy, the interaction of multiple cations leads to lattice distortions, and the sintering and annealing process induces the creation of oxygen vacancies, which significantly affect thermoelectric properties. The highest ZT (0.20) was obtained at a lanthanum content of 0.19 (ΔS_Conf=11.483 J/mol/K). This work provides theoretical and experimental bases for optimizing the thermoelectric properties of the materials by using high entropy design.