Synthesis and Characterization of New Ceramic Thermoelectrics Implemented in a Thermoelectric Oxide Module

Novel thermoelectric oxides were developed, produced, and characterized to demonstrate their promising thermoelectric conversion potential in a ther-moelectric converter. Four-leg thermoelectric oxide modules were fabricated by combining p- and n-type oxide thermoelements made of pressed polycrys-talline GdCo0.95Ni0.05O3 and CaMn0.98Nb0.02O3, respectively. In these mod-ules, the p- and n-type thermoelements were connected electrically in series and thermally in parallel. The materials were joined by electrical contacts consisting of a Ag/CuO composite material. Fairly good thermal contacts were ensured by pressing the thermoelements between alumina substrates. Cross-sections of the alumina/Ag–CuO mixture/thermoelement interface were investigated by scanning electron microscopy. The temperature distribution across the module was monitored using K-type thermocouples and a micro-infrared (IR) camera. The open-circuit voltage and the load voltages of the module were measured up to a temperature difference of DT = 500 K while keeping the temperature of the cold side at 300 K. The output power and internal resistance were calculated. The characteristics of the module evalu-ated from electrical measurements were compared with respective values of the p- and n-type leg materials. An output power of 0.04 W at DT = 500 K led to a power density of 0.125 W/cm3, where the volume of thermoelectric material was determined by a cross-section of 4 mm 9 4 mm and a leg length of 5 mm