A squeeze on the perovskite structure improves the thermoelectric performance of Europium Calcium Titanates. (December 2018)

• Record Type: Journal Article
• Authors: Xiao, X.; Widenmeyer, M.; Mueller, K.; Scavini, M.; Checchia, S.; Castellano, C.; Ma, D.; Yoon, S.; Xie, W.; Starke, U.; Zakharchuk, K.; Kovalevsky, A.; Weidenkaff, A.
• Is Part Of: Materials today physics. Volume 7(2018)
• Page Start: 96
• Page End: 105
• Publication Date: 2018-12
• Subjects: EuTiO3 -- Lattice deformation -- Thermoelectric transport properties; Materials science -- Periodicals; Physics -- Periodicals; Electronic journals; 530.41
• DOI: 10.1016/j.mtphys.2018.11.009
• Languages: English
• ISSNs: 2542-5293

Abstract

Abstract: Polycrystalline Eu1– x Ca x TiO3– δ (0 ≤ x ≤ 1) samples were synthesised to investigate the interrelations among the crystal structure, local structural disorder, and thermoelectric properties. The Ca 2+ substitution is locally modifying (squeezing) the crystal structure, resulting in distinct differences between the long-range and local scales, e.g., the sample with x = 0.2 shows a cubic structure in long-range scale, while tetragonal distortions are observed locally. Additionally, the contraction of the unit cell volume with an accompanying reduction of the overall symmetry facilitates the accommodation of smaller Eu 3+ (instead of Eu 2+ ). The lattice imperfections induced by Ca 2+ substitution significantly improve electron concentration and simultaneously dramatically reduce thermal conductivity (i.e., as large as 50% compared with pristine sample) at room temperature. The average thermoelectric figure of merit of Eu0.2 Ca0.8 TiO3– δ is enhanced by almost 100% compared with that of the pristine EuTiO3 . This work demonstrates that controlling lattice deformation offers new ways to enhance the thermoelectric performance of titanates. Graphical abstract: Highlights: For Eu1-x Cax TiO3– δ, the Ca 2+ substitution results in distinct differences between the long-range and local scales. Ca 2+ substitution modifies the band structure of Eu1-x Cax TiO3– δ compounds. Ca 2+ substitution significantly improve electron concentration and simultaneously dramatically reduce thermal conductivity. with The average thermoelectric ZT of Eu0.2 Ca0.8 TiO3– δ is enhanced by almost 100% compared with that of the pristine EuTiO3 .