Highly efficient bismuth telluride doped p-type Pb_0.13Ge _0.87Te for thermoelectric applications

Bi₂Te₃ doped p-type Pb_0.13Ge _0.87Te samples were prepared by hot pressing. We report on very high power factor values of ∼30 μW/cm K² at 500 °C, as were determined from Seebeck coefficient and electrical resistivity measurements. From dila-tometric characterization, the phase transition from the low temperature rhombohedral to the high temperature cubic NaCl structures, takes place at 373 °C. This transition is accompanied by a continuous and gradual change of the lattice parameters, as was observed by hot stage XRD, suggesting a good mechanical durability upon thermal cycling and operating in large thermal gradients. Rhombohedral distortion of the cubic NaCl structure of Pb _1-xGe_xTe upon cooling, characterized by changes in the interaxial angle α and the lattice parameter.