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    High performance Ca3-xAg0.3LaxCo4O9 materials for aerospace applications of thermoelectric devices
    (Springer, 2024) Sari, Mucahit Abdullah; Kilinc, Enes; Uysal, Fatih; Kurt, Huseyin; Celik, Erdal
    In the domain of aviation applications, the utilization of thermoelectric materials holds significant importance, particularly in regions characterized by notable thermal gradients, aimed at harnessing these gradients for electricity generation. This study advocates for the adoption of thermoelectric modules, specifically within the operational contexts of fixed-wing aircraft and satellites. These settings require resilient thermoelectric systems capable of effectively exploiting temperature differentials to enable electrical power generation, thus emphasizing the necessity of integrating such modules into their operational frameworks. Accordingly, this paper systematically elucidates the production and characterization of Ca3-xAg0.3LaxCo4O9 for thermoelectric applications in the aerospace sector. Ca3-xAg0.3LaxCo4O9 ceramics are synthesized via the sol-gel method employing Ca, Ag, La, and Co precursor materials. Distilled water serves as the solvent to dissolve the precursors, yielding homogeneous solutions. These solutions undergo magnetic stirring at 100 degrees C to achieve final homogeneity, with citric acid monohydrate introduced as a chelating agent to expedite xerogel formation. pH and turbidity measurements are conducted on the prepared solutions using a pH meter and turbidimeter, respectively. Following the gelation process, the resulting xerogel is dried at 200 degrees C for 2 h to eliminate moisture and undesirable gases. Subsequently, the dried powders are calcined at 800 degrees C for 2 h, yielding the final Ca3-xAg0.3LaxCo4O9 materials. The thermal, structural, microstructural, and thermoelectric properties of the materials are comprehensively characterized utilizing DTA-TG, FTIR, XRD, XPS, SEM, and thermoelectric measurement machines. It is ascertained that the produced semiconducting ceramic materials exhibit efficient suitability for thermoelectric generator production.
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    Production and development of ZnAlGeO semiconducting materials for thermoelectric generators in potential aerospace applications
    (Springer, 2024) Sari, Mucahit Abdullah; Kilinc, Enes; Uysal, Fatih; Kurt, Huseyin; Celik, Erdal
    This research aims to produce and develop semiconducting thermoelectric materials for thermoelectric generators in aerospace applications. In this context, ZnAlGeO powders were synthesized via the sol-gel method using precursor materials and a 20% toluene solution in ethanol as the solvent. Glacial acetic acid was added to accelerate gel formation. The pH and turbidity values of prepared solutions were measured using a pH meter and turbidimeter. After gelation, the obtained xerogel was dried at 200 degrees C for 9 h to remove moisture and undesired gases. Dried powders were calcined at 600 degrees C for 4 h in air, resulting in final ZnAlGeO materials. The pellets underwent thermal processing for 36 h at a temperature of 1350 degrees C, targeting the production of bulk samples within the n-type semiconductor category. Extensive characterization, including thermal, structural, microstructural, and thermoelectric properties, was conducted using various techniques such as DTA-TG, FTIR, XRD, XPS, SEM, and thermoelectric measurement devices. The study concludes that the produced semiconducting ceramic materials exhibit efficiency for thermoelectric generator production. Zn1-x-yAlxGeyO (x = 0.02, 0.04, and y = 0.02, 0.04) powders were synthesized by sol-gel method and densified under high-pressure cold pressing.Effects of dual doping on thermoelectric properties of Zn1-x-yAlxGeyO (x = 0.02, 0.04, and y = 0.02, 0.04) were investigated.Thermoelectric performances of Zn1-x-yAlxGeyO (x = 0.02, 0.04, and y = 0.02, 0.04) are enhanced by dual doping.Promising Zn1-x-yAlxGeyO (x = 0.02, 0.04, and y = 0.02, 0.04) oxide materials for energy harvesting and conversion technologies, particularly in aerospace applications.