  In this work, the possibility of using niobium oxide recovered from tailings
from the Penouta Sn-Nb-Ta deposit (located at the North of Spain) as starting
material for growing microstructures is demonstrated. The properties of the
starting material have been studied to understand its crystal structure,
quality and purity. Recovered niobium oxide powders are mainly of TT-Nb2O5.
These powders have been used to grow Nb22O54 microrods by an evaporation method
in an argon atmosphere. Different characterization techniques (X-Ray
diffraction, scanning electron microscopy, micro-Raman spectroscopy,
luminescence) have been used to determine the properties of Nb22O54 microrods,
mainly focusing on the crystal quality and refractive index. The present study
opens the way to the transformation of waste (mine tailings) into a material of
high technological value as niobium oxide, and its reintroduction into the
value chain for a wide range of applications, from coatings to batteries and
supercapacitors.
