Ultra low thermal conductivity of disordered layered p-type bismuth telluride

Disordered layered p-type bismuth telluride was obtained by high pressure (1 GPa) and high strain deformation along the c-axis direction of commercially available single crystals. After initial deformation the p-type bismuth telluride flakes were subsequently fully densified by cold pressing (800 MPa at room temperature). As a result of the severe plastic deformation, the samples showed highly anisotropic electrical and thermal conductivities. In particular, the thermal conductivity measured along the pressing direction was as low as 0.34 W m-1 K-1, which is one of the lowest values reported for fully dense p-type bismuth telluride. The full set of thermoelectric properties of the disordered bismuth antimony telluride is critically discussed.