NbO/Nb2O5 core–shells by thermal oxidation |
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Authors: | Cláudio Nico Luís Rino Mariana Matos Rui Monteiro Florinda M Costa Teresa Monteiro Manuel PF Graça |
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Affiliation: | 1. Department of Physics & I3N, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal;2. KEMET Electronics, Werner von Siemens 1, Évora, 7005-639 Portugal Campus Universitário de Santiago, 3810-193 Aveiro, Portugal |
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Abstract: | Niobium oxides have been reported as an alternative to tantalum, and its oxide, for the production of capacitors, but these materials still require a further and exhaustive study. Understanding the dynamics of the oxidation process from NbO to Nb2O5 is essential to explain and control the properties of a niobium oxide based capacitors. In situ XRD analysis of NbO powders was performed from 100 to 1100 °C, which showed a temperature range where only amorphous phase is present. The capacitor anodes, formed from the same type of NbO powders, were then heat-treated in air from room-temperature (RT) to 550 °C and recorded with a video camera to see the colour shift. The presence of core–shell structures and the increase of the shell thickness/amount with temperature are visible in SEM. Finally, in situ spectroscopy studies were performed, in order to observe the interference spectra which are responsible for the observed colours. |
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Keywords: | Niobium oxide Core–shell In situ XRD Raman Interference Structural colour |
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