Estudo da síntese e caracterização do niobato de cobre via método sol-gel a partir da preparação do precursor de nióbio

Abstract

Copper niobate (CuNb₂O₆) has garnered increasing scientific interest due to its properties and technological applications, ranging from solar cells to microwave devices and infrared lasers. Considering the need to develop simpler and more cost-effective methodologies for its production, this study investigated the synthesis of CuNb₂O₆ using the protein-based sol-gel method, a wet chemical route that remains relatively unexplored for the formulation of this material. The production of the niobium precursor constitutes the central focus of this study, as it represents a fundamental step toward the efficient synthesis of copper niobate. This approach stands out as a sustainable alternative, starting with the preparation of the ammonium oxalate niobium precursor, obtained through fusion and complexation processes, along with the use of commercial copper nitrate. Both precursors exhibit high solubility in water, and gelatin was employed as a chelating and polymerizing agent, providing greater control over material formation. The resulting gels underwent controlled thermal treatments, being calcined in a muffle furnace at temperatures of 600 °C, 700 °C, 800 °C, 900 °C, and 1000 °C for three hours, with a heating rate of 5 °C/min. The samples were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Spectroscopy (EDS), in addition to Thermogravimetric Analysis (TGA) for assessing the niobium oxalate. The results revealed that at 600 °C, CuNb₂O₆ was fully formed in the monoclinic phase, whereas increasing the temperature to 1000 °C favored predominant crystallization in the orthorhombic phase, highlighting the structural transition of the material. In addition to the effectiveness in producing copper niobate, the adopted methodology proved to be efficient in significantly reducing both the temperature and synthesis time for both crystalline structures. The obtained samples exhibited high purity, absence of contamination, and characteristic morphologies consistent with data reported in the literature, reinforcing the potential of this method as a promising alternative for CuNb₂O₆ synthesis.