Oxide-Based Thermoelectric Generator for High-Temperature Application Using p-Type Ca3Co4O9 and n-Type In1.95Sn0.05O3 Legs

Abstract

Abstract A thermoelectric generator couples an entropy current with an electrical current in a way, that thermal energy is transformed to electrical energy. Hereby the thermoelectric energy conversion can be described in terms of fluxes of entropy and electric charge at locally different temperature and electric potential. Crucial for the function of a thermoelectric generator is the sign and strength of the coupling between the entropy current and the electrical current in the thermoelectric materials. For high-temperature application, tin-doped indium oxide (In1.95Sn0.05O3) and misfit-layered calcium cobalt oxide (Ca3Co4O9) ceramics were used as n- and p-type legs. The n-type material reaches a power factor of 6.8 μ W ⋅ c m − 1 ⋅ K − 2 $$6.8\,{\rm{\mu W}} \cdot {\rm{c}}{{\rm{m}}^{- 1}} \cdot {{\rm{K}}^{- 2}}$$ at 1,073 K and a figure of merit ZT of 0.07. The p-type material reaches 1.23 μ W ⋅ c m − 1 ⋅ K − 2 $$1.23\,{{\rm \mu W}} \cdot {\rm{c}}{{\rm{m}}^{- 1}} \cdot {{\rm{K}}^{- 2}}$$ and a figure of merit ZT of 0.21 at 1,073 K. A thermoelectric generator consisting of ten legs was characterized for different invested temperatures. It delivers 4.8 mW maximum power output and a electrical power density of 2.13 m W × c m − 2 $$2.13\,{\rm{mW \times c}}{{\rm{m}}^{{\rm{- 2}}}}$$ when the hot side is at 1,073 K and a temperature difference of 113 K is applied.