Transport and thermoelectric properties of hot-pressed SnSe$_{\mathrm{2}}$

Recently, SnSe has been reported as ultralow thermal conductivity material which make it become a very high thermoelectric fingure of merit ZT material, up to 2.6 at 923 K. But, it is hard to use SnSe for applications in high temperature range because SnSe decomposes at 700 K. Therefore, searching for crystalline materials with high ZT value at lower temperature is still an attracted field of research. SnSe$_{\mathrm{2}}$ is also 2D material which is expected to have low lattice thermal conductivity. However, less is known about thermoelectric property of SnSe$_{\mathrm{2}}$. Eutectic SnSe$_{\mathrm{2}}$-Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ has been repoted as a promsising low-temperature thermoelectric material with ZT$=$0.56 at 593 K. Here, we prepared the polycrystalline SnSe$_{\mathrm{2}}$ using hot pressure method. At temperature range up to 573 K, it exhibited an anisotropic n-type charge carrier. Ultra low thermal conductivity is achieved along parallel direction, however, ZT value is still very low whose maximum was 0.045 at 573 K due to low electrical conductivity, and increased with temperature. Our work showed the possibility to enhance ZT of SnSe$_{\mathrm{2}}$ polycrystalline via n- and p-type doping experiments.