Niobium oxide and tantalum oxide micro- and nanostructures grown using material recovered from mining tailings

: Niobium and tantalum-based oxides were recovered from mining tailings. These oxides were used as starting material for growing micro- and nanostructures by the evaporation method. The morphology and crystal structure of the final oxides were evaluated using X-ray diffraction (XRD), micro-Raman spectroscopy, and scanning electron microscopy (SEM). After the thermal treatment, microrods of both oxides were obtained, which presented exotic stoichiometries Nb 22 O 54 and K 6 Ta 10.8 O 30 , respectively.