Compressive creep behavior of cast Bi2Te3

In thermoelectric devices, Bi2Te3 must be able to operate under high temperature gradients for very long times (years) without appreciable deformation, while being subjected to stresses created by internal thermal mismatch and external forces (e.g., vibrations). The deformation rate of cast, coarse-grained Bi2Te3 was measured under uniaxial compressive stresses from 2 to 16 MPa at temperatures between 400 and 500 °C. At all temperatures, a power-law behavior is observed, with a stress exponent n=3–6 and an activation energy of ∼145 kJ/mol. Significant differences in creep rates are observed in duplicate experiments, which may be due to anisotropic creep resistance in coarse-grained specimens. Bi2Te3 is brittle at 400 and 450 °C but shows some compressive ductility at 500 °C, indicating that hot forging may be possible.