Abstract
The present challenge with all-oxide thermoelectric modules is their poor durability at high temperatures caused by the instability of the metal-oxide interfaces at the hot side. This work explains a new module concept based on a hybrid p–n junction, fabricated in one step by spark plasma co-sintering of Ca3Co4–xO9+δ (CCO, p-type) and CaMnO3−δ/CaMn2O4 (CMO, n-type). Different module (unicouple) designs were studied to obtain a thorough understanding of the role of the in situ formed hybrid p–n junction of Ca3CoMnO6 (CCMO, p-type) and Co-oxide rich phases (p-type) at the p–n junction (>700 °C) in the module performance. A time-enhanced performance of the modules attributed to this p–n junction formation was observed due to the unique electrical properties of the hybrid p–n junction being sufficiently conductive at high temperatures (>700 °C) and nonconductive at moderate and low temperatures. The alteration of module design resulted in a variation of the power density from 12.4 (3.1) to 28.9 mW/cm2 (7.2 mW) at ΔT ∼ 650 °C after 2 days of isothermal hold (900 °C hot side). This new concept provides a facile method for the fabrication of easily processable, cheap, and high-performance high-temperature modules.
Highlights
IntroductionWaste heat released during high-temperature processes (e.g., in the metallurgical industry) is significant with respect to costand energy-effective production.[1] Thermoelectric generators (TEGs) convert heat directly into electrical energy, representing promising technology for waste heat harvesting
Waste heat released during high-temperature processes is significant with respect to costand energy-effective production.[1]
This paves the way for oxide-based Thermoelectric generators (TEGs), which provide chemical and thermal stability at high temperatures, and in addition are low-cost and environmentally friendly.[4]
Summary
Waste heat released during high-temperature processes (e.g., in the metallurgical industry) is significant with respect to costand energy-effective production.[1] Thermoelectric generators (TEGs) convert heat directly into electrical energy, representing promising technology for waste heat harvesting. The materials which constitute these devices are often toxic and expensive metals and alloys,[2,3] and their use is hampered by severe limitations due to oxidation and low melting temperatures This paves the way for oxide-based TEGs, which provide chemical and thermal stability at high temperatures, and in addition are low-cost and environmentally friendly.[4] To date, the electrical output power of oxide-based TEGs is generally lower than that of the state-ofthe-art TEGs.[5] the output power is not always the key parameter to evaluate TE modules. TE modules, which generate a moderate electric power and possess good durability, are recognized as potential power sources for wireless sensors that could continuously operate at elevated temperatures.[6]
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