Low thermal conductivity of SrTiO <sub>3</sub> −LaTiO <sub>3</sub> and SrTiO <sub>3</sub> −SrNbO <sub>3</sub> thermoelectric oxide solid solutions
Yuqiao Zhang, Hai Jun Cho, Kenyu Sugo, Masashi Mikami, Sungmin Woo, Myung‐Chul Jung, Yao‐Hua Zhuang, Bin Feng, Yu‐Miin Sheu, Woosuck Shin, Woo Seok Choi, Myung Joon Han, Yuichi Ikuhara, Hiromichi Ohta
Abstract
Abstract Electron‐doped SrTiO 3 has been attracting attention as oxide thermoelectric materials, which can convert wasted heat into electricity. The power factor of the electron‐doped SrTiO 3 , including SrTiO 3 ‐LaTiO 3 and SrTiO 3 ‐SrNbO 3 solid solutions, has been clarified. However, their thermal conductivity ( κ ) has not been clearly identified thus far. Only a high κ (>12 W m −1 K −1 ) has been assumed from the electron contribution based on Wiedemann–Franz law. Here, we show that the κ of the electron‐doped SrTiO 3 is lower than the assumed κ , and its highest ZT exceeded 0.1 at room temperature. The κ slightly decreased with the carrier concentration ( n ) when n is below 4 × 10 21 cm −3 . In the case of SrTiO 3 ‐SrNbO 3 solid solutions, an upturn in κ was observed when n exceeds 4 × 10 21 cm −3 due to the contribution of conduction electron to the κ . On the other hand, κ decreased in the case of SrTiO 3 ‐LaTiO 3 solid solutions probably due to the lattice distortion, which scatters both electrons and phonons. The highest ZT was 0.11 around n = 1 × 10 21 cm −3 . These findings would be useful for the future design of electron‐doped SrTiO 3 ‐based thermoelectric materials.