Structural characterization of Brazilian niobium pentoxide and treatment to obtain the single phase (H-Nb2O5)

Abstract Studies indicate that the degree of polymorphism of niobium pentoxide (Nb2O5) is related to the origin of its extraction and that adequate heat treatments can improve its quality concerning the number of structural phases. In this study, the niobium pentoxide extracted from the region of the Triângulo Mineiro in the state of Minas Gerais in Brazil was heat treated and its structural characterization reveals to obtaining the single monoclinic phase (H-Nb2O5). The thermal treatments were carried out from 900 to 1150 °C and the desired single-crystal phase sample was obtained with the treatment at 1100 °C. The treated material was characterized by Dynamic Light Scattering (DLS), and its morphology by scanning electron microscopy (SEM). X-ray diffraction (XRD) and Rietveld refinement show the presence of the crystalline phase and a good agreement between the experimental and the calculated results were obtained. Functional groups, characteristic bands, and peaks were analyzed by infrared spectroscopy using Fourier Transform with Photoacoustic Detection (FTIR-PAS) and Raman spectroscopy. Thermal analysis was also made using thermogravimetric analysis (TGA), differential thermal analysis (DTA), and dilatometry techniques.