EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Niobium oxides have proved to have excellent properties for use in coatings, photocatalysis or energy storage and sensing devices. Added benefits of the use of these niobium oxides are their biocompatibility, non-toxicity and resistance to corrosion. This can increase the lifetime of the material and facilitate the recuperation if it is used in liquid environments (for example, used as photocatalyst to clean contaminated water). The performance of these oxides in the different applications can be improved by tuning the electrical conductivity, which can be achieved by introducing changes in the concentration of oxygen. Typically, it has been observed that Nb and NbO have a metallic character, NbO$_{2}$ is a semiconductor and Nb$_{2}$O$_{5}$ is typically insulator [1]. Less studied are the non-estoquiometric phases (Nb$_{2}$O$_{5-δ}$), but they present superior conduction performance, allowing to use them as transparent conductive oxides [2], as efficient photocatalysts [3] or for energy storage devices [4].
In this work, we have prepared ceramic pellets of niobium oxide with different crystallographic phases and oxygen concentration. We have studied the effect of fs-laser irradiation (350-fs) with different repetition rates and energies on the electrical and optical properties of the niobium oxides, showing that fs-laser irradiation can be used to control the formation of oxygen-deficient compounds.

[1] C. Nico et al. "Niobium oxides and niobates physical properties: Review and prospects." Progress in Materials Science, 80, 1-37 (2016).
[2] T. Ohsawa et al. "An n-type transparent conducting oxide: Nb$_{12}$O$_{29}$." The Journal of Physical Chemistry C, 115, 16625-16629 (2011).
[3] W. Zhao et al. "Black Nb$_{2}$O$_{5}$ nanorods with improved solar absorption and enhanced photocatalytic activity." Dalton Transactions, 45, 3888-3894 (2016).
[4] F. Liu et al. "Binding Sulfur‐Doped Nb$_{2}$O$_{5}$ Hollow Nanospheres on Sulfur‐Doped Graphene Networks for Highly Reversible Sodium Storage." Advanced Functional Materials, 28, 1800394 (2018).