Pressure induced enhancement of anharmonicity and optimization of thermoelectric properties in n-type SnS

Pressure serves as a powerful approach to regulating the thermal conductivity of materials. By applying pressure, one can alter the lattice symmetry, atomic spacing, and phonon scattering mechanisms, thereby exerting a profound influence on thermal transport properties. SnS, sharing the same crystal structure as SnSe, has often been overlooked due to its higher lattice thermal conductivity. While extensive efforts have been dedicated to enhancing the power factor of SnS through doping, its thermal transport properties remain underexplored, limiting its potential as a thermoelectric material. In this study, we investigated the impact of pressure modulation on the thermoelectric performance of SnS. Remarkably, the application of negative pressure significantly enhanced its thermal transport characteristics, leading to a reduction in the lattice thermal conductivity (<inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML249722324.png" baseline="-3.5" display="inline" id="mathml_M1" overflow="scroll"><mml:mrow class="MJX-TeXAtom-ORD"><mml:mstyle><mml:mrow><mml:msub><mml:mrow><mml:mi>&#x03BA;</mml:mi></mml:mrow><mml:mrow><mml:mi>L</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:mstyle></mml:mrow></math></inline-formula>) along the <inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML249722325.png" baseline="-0.5" display="inline" id="mathml_M2" overflow="scroll"> <mml:mrow class="MJX-TeXAtom-ORD"><mml:mstyle><mml:mi>a</mml:mi></mml:mstyle></mml:mrow></math></inline-formula> axis to 0.23 W/(m&#x00B7;K) at 800 K, on par with that of SnSe. Despite the negligible improvement in carrier mobility under negative pressure, the electronic transport properties were preserved within an acceptable range. Most notably, a maximum <i>ZT</i> value of 2.7 was achieved along the <inline-formula><math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="c:\heptemp\HML249722087.png" baseline="-0.5" display="inline" id="mathml_M3" overflow="scroll"><mml:mrow class="MJX-TeXAtom-ORD"><mml:mstyle mathcolor="khaki"><mml:mi>a</mml:mi></mml:mstyle></mml:mrow></math></inline-formula> axis at 800 K, marking a substantial advancement in the thermoelectric performance of n-type SnS.