Oxide transversal multilayer thermoelectric generators

Reference Presenter Authors
08-022 Jörg Töpfer Töpfer, J.(Ernst-Abbe-Hochschule jena); Reimann, T.(Ernst-Abbe-Hochschule Jena); Schulz, T.(Eranst Abbe Hochschule Jena); Bochmann, A.(Eranst Abbe Hochschule Jena); Capraro, B.(Fraunhofer IKTS); Teichert, S.(Ernst Abbe Hochschule Jena); Thermoelectric generators (TEG) exhibit high potential as energy sources transforming waste heat into electricity. Oxides represent a versatile class of thermoelectric materials. Unfortunately, their thermoelectric performance is inferior compared to classic semiconductor thermoelectrics (lower ZT values). On the other hand, oxide thermoelectrics exhibit stability at increased operating temperatures; they are low-price and environmentally friendly. Ceramic TEGs require p- and n-conducting oxides with high Seebeck coefficient and high electrical and low thermal conductivity. Miniaturized modules can be prepared as multilayer TEGs from thermoelectric oxide green tapes. Examples of oxides discussed in detail include n-type CaMnO3, p-type La2CuO4 and Ca3Co4O9. The shrinkage is adapted using additives to enable co-firing of different materials as required for a multilayer process. The synthesis of individual oxides, their sintering behavior and thermoelectric properties will be discussed. Multilayer TEG’s were fabricated by stacking thermoelectric oxide green sheets, screen-printing of metal conductors and insulation layer, and co-firing. However, co-firing of such multilayer thermoelectric generators (MLTEG) consisting of four different materials turned out to be very challenging. We report on a new concept of oxide-based transversal multilayer thermoelectric generator (TMLTEG), which focuses on the combination of one thermoelectric oxide only (either p- or n.-type) with metal electrodes. The electrode are printed as stripes, oriented at a certain angle to the current flow. This enables the use of the transversal thermoelectric effect, with the directions of the heat and charge flow perpendicular to each other. Several TMLTEGs were fabricated, able to provide some mW power at ?T = 100 K or less. They exhibit potential as autonomous energy sources in the low-power range to drive sensors and microsystems.
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