Raman spectra of niobium oxides

Enhanced Raman scattering in thermally poled sodium-niobium borophosphate glasses

“…This is in comparison to edgesharing NbO 6 octahedra ͑highly distorted, with Nb-O bonds ranging from 1.7 to 2.3 Å͒, which have the symmetric stretching mode in the range of 650-750 cm −1 . 17 Based on the above considerations, the additional spectral changes in the NLO layer indicated by an intensity decrease at 820 cm −1 and increase at 720 cm −1 ͑see Fig. 5͒ may arise from complex structural reorganizations in the phosphoniobate glass matrix.…”

The structure of niobium and tantalum oxides processed by concentrated light flux

“…Hence, the CLF-treated oxides reveal the micro-and nanostructures ('micro-cracks' and 'nanocracks'), which are known to suppress the effect of thermal expansion [3,4]. Both the niobium and tantalum oxides have the phases of variable compositions [5,6,7]. The structures characterised by different Nb(Ta)/O ratios and thermal histories may belong to modifications of different symmetry space groups.…”

“…The X-ray diffraction analysis cannot identify the atomic coordinates of the structure of real samples. Since the calculations of lattice dynamics are also impossible, the Raman spectra remain the only way to identify the real structures of Nb 2 O 5 and Та 2 O 5 [7,8,9]. Due to complexity of our structures and some amount of endless chains, blocks, chain parts, and octahedral and tetrahedral blocks of different crystallographic systems [6,[9][10][11][12][13], the Raman bands of the niobium and tantalum oxides can be correctly assigned only in the case of single-crystalline samples and a certain scattering geometry.…”

Desenvolvimento de materiais nanoestruturados à base de óxido de nióbio para aplicação em fotônica

“…As (TERAO, 1965;MCCONNELL et al, 1976;KO e WEISSMAN, 1990;NOWAK e ZIOLEK, 1999 : (A) 90Si-10Nb tratada termicamente a 900°C, (B) 70Si-30Nb tratada termicamente 900°C, (C) 70Si-30Nb tratada termicamente a 1000°C, (D) 70Si-30Nb tratada termicamente a 1100°C, (E) 50Si-50Nb tratada termicamente 900°C, (F) 50Si-50Nb tratada termicamente 1000°C, e (G) 50Si-50Nb tratada termicamente 1100°C por 10 horas. Detalhe: difração de elétrons mostrando a cristalização dos nanocompósitos.…”

“…A fase M, que foi identificada nos materiais do presente trabalho, cristaliza-se a 800°C, tem sido descrita na literatura como uma fase H mal cristalizada e muitos autores tem reconhecido que os polimorfos são essencialmente os mesmos. A discussão sobre essas duas fases cristalinas será retomada nas seções referentes à caracterização estrutural (TERAO, 1965;MCCONNELL et al, 1976;KO e WEISSMAN, 1990;NOWAK e ZIOLEK, 1999 (TANABE, 1990;ZIOLEK, 2003;NAKAJIMA et al, 2010;DI SERIO et al, 2012;SREETHAWONG et al, 2013), eletrocromismo (AEGERTER, 2001;BUENO et al, 2001;ROSARIO e PEREIRA, 2005;ROMERO et al, 2009), sensores (CHAMBON et al, 1997FANG et al, 2011;WANG et al, 2012;RANI et al, 2013) e materiais biocompatíveis para próteses (VELTEN et al, 2004;OCHSENBEIN et al, 2008;NASCIMENTO et al, 2011;RAMÍREZ et al, 2011), além das aplicações fotônicas que serão discutidas a seguir.…”