Enhancing the thermoelectric properties of Sr1- xPr2 x/3? x/3TiO3± ? through control of crystal structure and microstructure.

ABSTRACT: A-site deficient perovskites are among the most important n-type thermoelectric oxides. Ceramics of Sr1- xPr2 x/3? x/3TiO3 ( x?=?0.1-1.0) were prepared by solid-state reaction at 1700-1723?K using highly reducing atmospheres. Samples with the highest Sr content had a cubic crystal structure [Formula: see text]; incorporating Pr with A-site vacancies led to a reduction in symmetry to tetragonal ( I4/mcm) and then orthorhombic ( Cmmm) crystal structures. HRTEM showed Pr2/3TiO3 had a layered structure with alternating fully and partially occupied A-sites and a short-range order along the (100) direction. Electrical conductivity was highest in samples of high symmetry ( x???0.40), where the microstructures featured core-shell and domain structures. This enabled a very high power factor of approximately 1.75?×?10-3?W?m-1?K-2 at 425?K. By contrast, at high Pr content, structural distortion led to reduced electron transport; enhanced phonon scattering (from mass contrast, local strain and cation-vacancy ordering) led to reduced, glass-like, thermal conductivity. Carbon burial sintering increased the oxygen deficiency leading to increased carrier concentration, a maximum power factor of approximately 1.80?×?10-3?W?m-1?K-2 at 350?K and thermoelectric figure of merit of 0.26 at 865?K. The paper demonstrates the importance of controlling both crystal structure and microstructure to enhance thermoelectric performance. This article is part of a discussion meeting issue 'Energy materials for a low carbon future'.

SUBMITTER: Ekren D 

PROVIDER: S-EPMC6635635 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature