Sol-gel fabrication of thermoelectric P-type Ca_2.5Ag_0.3Ce_0.2Co₄O₉ materials for aerospace applications

The article provides a comprehensive description of the synthesis and characterization of Ca2.5Ag0.3Ce0.2Co4O9 semiconducting ceramics for potential application in thermoelectric generators, particularly in the aerospace industry. These materials were synthesized using the sol-gel method, with distilled water serving as the solvent and citric acid monohydrate incorporated into expedited gel formation. The pH and turbidity values of solutions were monitored through a pH meter and turbidimeter, respectively. The produced xerogel was subjected to drying at 200 degrees C for 2 h in an air atmosphere to remove residual moisture and volatile by-products. The desiccated powders were then heat-treated at 800 degrees C for 2 h under ambient air conditions, yielding the final Ca2.5Ag0.3Ce0.2Co4O9 compound. Thermal processing of the resulting pellets was carried out at 900 degrees C for 24 h to fabricate bulk samples. Comprehensive characterization was performed to assess thermal, structural, microstructural, and thermoelectric behaviors via DTA-TG, XRD, XPS, SEM, and TM machines. It was found that at 800 degrees C, a maximum power factor of .24 mW/mK-2 was achieved, derived from a Seebeck coefficient of 214.30 mu V/K and electrical resistivity of 19.05 m Omegacm at the same temperature. The synthesized ceramic materials exhibit promising thermoelectric efficiency, making them suitable for thermoelectric generator production.