Enhancing figure-of-merit of n-type Bi$_{2}$Te$_{3-x}$Se$_{x}$

Themoelectric materials with high dimensionless figure-of-merit (ZT) are greatly demanded in energy industry, among which bismuth telluride (Bi$_{2}$Te$_{3})$ exhibits decent ZT around room temperature. However, thermal conductivity of Bi$_{2}$Te$_{3}$ is still high which limits its wider use for low temperature cooling devices. Here we investigate nanostructured bulk n-type Bi$_{2}$Te$_{3-x}$Se$_{x}$ by reducing the thermal conductivity via increased phonon scattering of the significantly increased grain boundaries due to nano size grains. We first make alloyed nanopowders by mechanical alloying a mixture of elements with the right ratio and then 100{\%} nanostructured samples by hot press.