Production of thermoelectric films by ultrasonic spray pyrolysis method

In this thesis study, it was aimed to conduct research on the thermoelectric properties of powders obtained from the different pH solutions of Ca3Co4O9 and CaMnO3 thermoelectric materials and the films obtained from these solutions by way of Ultrasonic Spray Pyrolysis (USP) system. In this scope, stoichiometric and non-stoichiometric recipes were calculated after which the solutions of these recipes were prepared in acidic, basic and neutral environments. The sintering behaviors were then obtained for the powders obtained from these solutions and the films acquired from the identified solutions. Thermal, FTIR, phase analysis and microstructure analyses were conducted for the characterization of the obtained powder and film materials after which their optical, thermoelectric properties and efficiencies were measured. It was identified that homogenization is required for single phase production in powder sintering and that homogeneity can be attained through pellet sintering-grinding after powder sintering-grinding based on the number of repetitions. It was illustrated that double or triple sintering is required instead of single sintering for homogeneous phase distribution in sintering. Based on the thermal and phase analysis results of Ca3Co4O9 powder materials, it was identified that the Ca3Co4O9 phase is disrupted at temperatures exceeding 800 °C. Hence, all three sinterings for Ca3Co4O9 powder materials were conducted at 800 °C, whereas single sintering was conducted at the same temperature for film materials. First sintering temperature was 1000 °C for CaMnO3 powder materials whereas the second sintering temperature was 1300 °C. However, all three sinterings of CaMnO3 films were conducted at de 900 °C. The heater table temperature in the USP system for Ca3Co4O9 and CaMnO3 films were identified respectively as 400 and 500 °C. In conclusion; it was identified that the thermoelectric measurements obtained for Ca3Co4O9 and CaMnO3 powder and film materials are in accordance with the findings in literature and that both powder and film thermoelectric materials can be manufactured economically using the USP system.