Thermal and structural analysis of germanate glass and thin films co-doped with silver nanoparticles and rare earth ions with insights from visible and Raman spectroscopy
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2016-11-01
Autores
Carvalho, E. A.
Freitas, A. M.
Silva, G. H.
Bell, M. J.V.
Kassab, L. R.P. [UNESP]
Anjos, V.
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Resumo
This paper reports on the thermal and optical properties of germanate glasses GeO2–PbO co-doped with silver nanoparticles and rare earth ions (Tm3+, Er3+ and Yb3+) with a focus on the thermal diffusivity (D). The presence of rare earth ions and nanoparticles is evidenced by absorption spectra and TEM images, respectively. Additionally, a structural comparison between thin films and bulk glass with the same nominal composition is given. It is found that D increases up to 20% in samples where nanoparticles are present, although their quantity corresponds only to a volume fraction of 1.7%. Therefore, such enhancement could be associated with the nanoparticles. Nevertheless, a Raman analysis revealed a structural change after the thermal treatment used for the nucleation of the nanoparticles. A decrease in the intensity of the band at 534 cm−1 in the Raman spectra is interpreted as the disruption of the 3-membered rings of the GeO4 tetrahedra. The Raman analysis also revealed the formation of small crystals of α-GeO2 type quartz and the adsorption of carbon dioxide on the surface of the silver nanoparticles inserted in the germanate thin film.
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Palavras-chave
Germanate, Nanoparticles, Raman scattering, Rare earths, Thermal diffusivity, Thermal lens
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Vibrational Spectroscopy, v. 87, p. 143-148.