New solution method to produce high performance thermoelectric ceramics: A case study of Bi-Sr-Co-O

Bi₂Sr₂Co_1.8O_x ceramics have been synthesized through a solution method involving the addition of polyethyleneimine as coordinating agent for the metallic cations. From these powders, bulk sintered materials have been prepared. Microstructure has been studied by means of scanning electronic microscopy (SEM) and it has shown that samples are mainly composed by the thermoelectric phase, with very small amounts of secondary phases. Electrical resistivity measurements showed very small values (around 21 mΩ cm at room temperature), nearly constant with temperature, while thermopower increases rapidly to values higher than 200 μV/K at 650 °C. Power factor value at 50 °C is about 0.08 mW/K² m and 0.20 at 650 °C, which makes this ceramic a potential material for power generation applications.