Sol-Gel Synthesis of Ca2.8Pr0.2Co4O9 Powders with Thermal and Structural Characterization

In this paper, Ca2.8Pr0.2Co4O9 powders were synthesized by sol-gel method and thermal and structural characterization of the powders were systematically examined for high temperature thermoelectric generator applications. Solution characteristics of precursors were examined by Turbidity and pH measurements using a turbidimeter and a pH meter. Differential Thermal Analysis-Thermogravimetry (DTA-TG) was used to specify appropriate thermal regime of the powders for calcination process. Chemical structure and reaction type of intermediate temperature products were defined by Fourier Transform Infrared (FTIR) Spectroscopy. Structural properties of the powders were implemented by X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) was used to specify chemical composition and empirical formula of the elements existed within the powders. Drying, oxidation and phase transformation temperatures of the powders were optimized according to the DTA-TG and FTIR results. Considering the DTA curve, endothermic and exothermic reactions took place between temperature interval of 270 °C and 480 °C due to drying process at 200 °C. In addition, phase formation peaks of Ca2.8Pr0.2Co4O9 powders can be observed in the XRD study. It can be seen from the phase spectrum that 2? peaks correspond to the literature and coincide with typical Ca3Co4O9 peaks.