Several crystal structures of niobium-based materials are currently being studied. In this work, for the first-time a mixture of H4Nb2O7 and Nb2O5 materials was obtained from ammonium niobate oxalate using the urea hydrolysis reaction in a hydrothermal synthesis. The techniques used for characterization, such as X-ray diffraction (XRD), Rietveld refinement, Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and High-Resolution Transmission Electron Microscopy (HRTEM), confirmed a combination of pyrochlore-type H4Nb2O7 and pseudohexagonal TT-Nb2O5 phases, with distinct nanostructures and anisotropic growth in the TT- Nb2O5 phase, in addition to controlling phase fractions by synthesis time. These discoveries suggest potential applications in various environmental applications due to the material’s adsorptive capacity.