Optimization of All-Oxide 2D Layered Thermoelectric Device Fabricated by Plasma Spray

Harvesting waste energy using thermoelectric (TE) principles is a key technology that increases overall power conversion and efficiency from combustion-based energy generation systems. However, design restrictions of commercially available thermoelectric devices and toxicity of commercial thermoelectric materials currently limit large-scale deployment. Additive and multilayered design and manufacturing of thermoelectric modules are a potential pathway to overcome current design restrictions as it enables to implement the device directly to the engineering structures with direct access to waste heat. Plasma spray is the chosen technology in this work to fabricate such patterned and layered TE devices, using as p-type Ca₂Co₂O₅ and the n-type material TiO_2-x. The optimization of thermoelectric leg geometry results in a maximum power density output of 1.9 × 10⁻⁴ W/cm² per couple and efficiency of 1.1% at 750 K. An important aspect of this TE device design is that it allows direct p-n contact, whereas the proportionality between p-n contact area and power output is demonstrated. A correlation between the coating thickness and nonlinear behavior of the thermoelectric voltage is also discussed, which is associated with the anisotropy degree of the n-type coating.