Journal
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
Volume 31, Issue 4, Pages 501-506Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.jeurceramsoc.2010.10.024
Keywords
D. Niobates; B. Fibres; C. Optical properties; C. Dielectric properties; Laser Floating Zone
Categories
Funding
- QREN/Compete - NbO [5309]
- FCT, Portugal [PTDC/CTM/66195/2006]
- FCT [SFRH/BD/45774/2008]
- Fundação para a Ciência e a Tecnologia [SFRH/BD/45774/2008] Funding Source: FCT
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Samples of Nb2O5 were prepared by laser floating zone (LFZ) technique and by solid-state reaction in order to study some of their physical properties as a function of synthesis conditions. Single crystals fibres were obtained by LFZ, while a structural orthorhombic to monoclinic phase transition was observed in samples sintered at temperature higher than 800 degrees C. Transmission optical spectroscopy and photoconductivity measurements allowed identifying a similar to 3.2 eV bandgap energy for the H-Nb2O5 monoclinic crystalline phase. Band gap shrinkage of similar to 100 meV was observed from 14K to RT. For the orthorhombic phase (T-Nb2O5), the photoconductivity measurements evidence a higher energy bandgap. The sintered samples have shown a broad recombination luminescence band at the orange/red spectral region while no luminescence was detected from the LFZ grown fibres. A dielectric constant of similar to 40 was found for the 800 degrees C and 1200 degrees C sintered pellets while that of 1000 degrees C reached four times that value. (C) 2010 Elsevier Ltd. All rights reserved.
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