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High niobium oxide content in germanate glasses: Thermal, structural, and optical properties
Author(s) -
Marcondes Lia Mara,
Maestri Sérgio,
Sousa Bianca,
Gonçalves Rogeria Rocha,
Cassanjes Fabia Castro,
Poirier Gael Yves
Publication year - 2018
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15215
Subject(s) - germanate , niobium , niobium oxide , materials science , crystallization , raman spectroscopy , oxide , analytical chemistry (journal) , differential thermal analysis , absorption spectroscopy , fourier transform infrared spectroscopy , alkali metal , niobium pentoxide , natural bond orbital , phase (matter) , mineralogy , inorganic chemistry , chemistry , chemical engineering , metallurgy , optics , physics , optoelectronics , organic chemistry , doping , diffraction , engineering , density functional theory , computational chemistry , chromatography
Niobium alkali germanate glasses were synthesized by the melt‐quenching technique. The ternary system (90‐ x )GeO 2 – x Nb 2 O 5 –10K 2 O forms homogeneous glasses with x ranging from 0 to 20 mol%. Samples were investigated by DSC and XRD analysis, FTIR and Raman spectroscopy, and optical absorption. Structural and physical features are discussed in terms of Nb 2 O 5 content. The niobium content increase in the glass network strongly modifies the thermal, structural and optical properties of alkali germanate glasses. DSC , Raman and FTIR analysis suggest niobium addition promotes NbO 6 groups insertion close to GeO 4 units of the glass network. XRD analysis also pointed out that samples containing high niobium oxide contents exhibit preferential niobium oxide‐rich phase after crystallization after heat treatment, which is similar to orthorhombic Nb 2 O 5 . Absorption spectra revealed high transmission range between 400 nm to 6.2 μm, added to a considerably decreased hydroxyl group content as the addition of niobium in the alkali germanate network. The niobium oxide‐rich phase crystallization process was studied and activation energy was determined, as well as nucleation and crystal growth temperatures and time for obtaining transparent glass‐ceramics.