<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>β</mml:mi><mml:mtext>−</mml:mtext><mml:msub><mml:mi>SrZrS</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>: A superior intermediate temperature thermoelectric through complex band geometry and ultralow lattice thermal conductivity

Abstract

The pursuit of high-performance thermoelectricity has generated an endless stream of suitable materials, but those having intrinsically low thermal conductivity are highly desirable for production. Here, we demonstrated intrinsically low lattice thermal conductivity (${\ensuremath{\kappa}}_{l}$) for the orthorhombic phase $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{SrZrS}}_{3}$, a chalcogenide perovskite. The weak interatomic interactions are noticed for ${\mathrm{SrS}}_{8}$ bicapped trigonal prism geometry, leading to the bond heterogeneity and thus an effective anharmonicity in the system. This anharmonicity facilitates the low ${\ensuremath{\kappa}}_{l}$. The average ${\ensuremath{\kappa}}_{l}$ value at 300 K is found to be $\ensuremath{\sim}1.26\phantom{\rule{0.16em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1\phantom{\rule{0.16em}{0ex}}}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$, while at 800 K it further reduces to a lower value of $\ensuremath{\sim}0.48\phantom{\rule{0.16em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1\phantom{\rule{0.16em}{0ex}}}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ due to enhanced phonon-phonon scattering. The presence of several valleys within a small energy offset from the primary conduction-band edge and a sort of pudding-mold-kind appearance make the band structure more complex. These band features in the conduction band facilitate the system with a high-power factor with $n$-type doping. Avoiding bipolar conduction is also confirmed via a large-band-gap value of \ensuremath{\sim}2.04 eV for $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{SrZrS}}_{3}$. Furthermore, significant phonon-phonon scattering is caused by the high anharmonic interaction resulting from the coupling of the acoustic and low optical frequency domains, substantiating the low ${\ensuremath{\kappa}}_{l}$. Additionally, the electron's lifetime at 300 K is \ensuremath{\sim}34 fs and its mobility is $\ensuremath{\sim}{10}^{2}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1\phantom{\rule{0.16em}{0ex}}}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. Thus, an impressive figure of merit $&gt;2$ is achieved for the intermediate temperature (600--800 K) at an experimentally feasible electron doping of $\ensuremath{\sim}{10}^{20}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}3}$, indicating that $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{SrZrS}}_{3}$ could be an excellent wide-band-gap thermoelectric material.

Topics & Concepts