Reducing the thermal conductivity while maintaining excellent electrical transport properties is crucial for enhancing the thermoelectric performance of SrTiO₃-based perovskites. Here, we successfully achieved this goal through precisely manipulating the configurational entropy. A series of Ca_0.25Nd_0.25Sr_0.5–x Ba_xTiO₃ (x = 0, 0.05, 0.15, 0.25) ceramics were successfully synthesized using the solid-state reaction combined with graphite burial sintering. It was discovered that structural defects from competing elements in the A-site not only slowed diffusion and hindered grain growth but also increased oxygen vacancies by creating additional gas transmission channels. The gradual decrease in carrier mobility with increasing entropy resulted in the degradation of electrical conductivity, while the Seebeck coefficient experienced a large enhancement due to band modification and increased carrier scattering. Meanwhile, multiscale defects, including point defects, local strain fields, dislocations, and grain boundaries, effectively scatter phonons, leading to a low lattice thermal conductivity of 1.73 W·m^–1·K^–1. Consequently, the sample with x = 0.15 exhibited a peak ZT of 0.15 at 900 K, reflecting a 148% enhancement compared to that of the matrix. In addition, the hardness increases with configurational entropy because of the chemical disorder, grain refinement, and increased defect concentration. The work emphasizes the importance of precise manipulation of configurational entropy, offering valuable insights for optimizing thermoelectric materials through entropy engineering strategy.

中文翻译：

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SrTiO3 钙钛矿的熵调控以增强热电和机械性能


在保持优异电传输性能的同时降低热导率对于提高 SrTiO₃ 基钙钛矿的热电性能至关重要。在这里，我们通过精确操纵构型熵成功地实现了这个目标。使用固相反应结合石墨埋藏烧结成功合成了一系列 Ca_0.25Nd_0.25Sr_0.5–x Ba_xTiO₃ （x = 0， 0.05， 0.15， 0.25） 陶瓷。研究发现，A 位点竞争元素的结构缺陷不仅减慢了扩散并阻碍了晶粒生长，而且还通过创造额外的气体传输通道来增加氧空位。随着熵的增加，载流子迁移率逐渐降低，导致电导率下降，而塞贝克系数由于能带修饰和载流子散射增加而大幅增强。同时，包括点缺陷、局部应变场、位错和晶界在内的多尺度缺陷有效地散射了声子，导致晶格热导率低至 1.73 W·m^–1·^K-1.因此，x = 0.15 的样品在 900 K 处的峰值 ZT 为 0.15，与基质相比提高了 148%。此外，由于化学无序、晶粒细化和缺陷浓度增加，硬度随着构型熵的增加而增加。这项工作强调了精确操纵构型熵的重要性，为通过熵工程策略优化热电材料提供了有价值的见解。