Fabrication of p-type synthesis of p-type Ca_2.7Ag_0.3Co₄O₉semiconducting materials for thermoelectric generators in aerospace applications

In aviation applications, thermoelectric materials play a crucial role in harnessing substantial thermal differentials to generate electrical signals. This study emphasizes the use of thermoelectric modules in fixed-wing aircraft and satellites, where robust systems are essential for effective power generation. The paper details the production and characterization of Ca_2.7Ag_0.3Co₄O₉ ceramics for aerospace thermoelectric applications. Using a sol-gel method with Ca, Ag, and Co precursors, homogeneous solutions were prepared, mixed, and stirred at 100 °C, with citric acid monohydrate added as a chelating agent. The xerogel formed was dried at 200 °C, calcined at 800 °C, and sintered at 900 °C for 24 h in air, yielding the final material. Extensive characterization using TG-DTA, FTIR, XRD, XPS, SEM, and thermoelectric measurement machines confirmed that the produced semiconducting ceramics are suitable for thermoelectric generator production. The synthesis of Ca₂.₇Ag₀.₃Co₄O₉ ceramic powders involved solution preparation (pH 1.51, turbidity 8.33 ntu), drying at 100 °C, combustion at 200 °C, calcination at 800 °C, and sintering at 900 °C. FTIR analysis confirmed the breakdown of O-H, N-O, and C-N bonds at 800 °C, forming the desired phase. XRD confirmed the crystalline nature and structural impact of Ag doping. XPS detected Ag, confirming p-type semiconductor synthesis. SEM revealed expected grain morphologies. Thermoelectric measurements at 800 °C showed a Seebeck coefficient of 208.40 μV/K, electrical resistivity of 14.59 mΩ cm, and a power factor of 0.50 mW/m·K². Furthermore, the low density and chemical stability of this oxide-based material offer additional advantages for lightweight, durable, and environmentally friendly applications in aerospace thermoelectric systems.