Rapid\nSynthesis of Sb<sub>2</sub>Si<sub>2</sub>Te<sub>6</sub> under High\nPressure with a Modulated Microstructure

Over\nthe past decades, thermoelectric materials have advanced significantly,\nyet materials such as Sb<sub>2</sub>Si<sub>2</sub>Te<sub>6</sub>,\nwhich are challenging to synthesize chemically, often require lengthy\nand complex preparation processes, hindering their development. In\nthis work, we prepare polycrystalline Sb<sub>2</sub>Si<sub>2</sub>Te<sub>6</sub> bulk from elemental precursors using a high-pressure\nsynthesis (HPS) method. This method offers significant advantages\nin efficiency and preparation duration. The applied pressure promotes\nan isotropic microstructure and regulates the thermoelectric properties\nby controlling precipitate contents, grain size, and twinning. Although\nan increase in thermal conductivity, mostly due to the notable increase\nin electrical conductivity, leads to less favorable thermal conductivity\nnear room temperature compared to samples prepared using conventional\nmethods, a beneficial reversal occurs at high temperatures. The polycrystalline\nSb<sub>2</sub>Si<sub>2</sub>Te<sub>6</sub> sample synthesized at 2\nGPa demonstrates a peak <i>ZT</i> value of 1.1 at 773 K,\noutperforming most pristine Sb<sub>2</sub>Si<sub>2</sub>Te<sub>6</sub> materials. This work demonstrates an efficient strategy for optimizing\nSb<sub>2</sub>Si<sub>2</sub>Te<sub>6</sub> performance and offers\na new synthesis pathway for other challenging thermoelectric materials.