Optical properties of holmium-doped in sol-gel silica glass

DOI

10.2991/msc-18.2018.33How to use a DOI?

Keywords

Holmium (Ho3+), sol-gel, annealing, Judd-Ofelt, photoluminescence

Abstract

In this work holmium (Ho3+)-doped in silica glass was prepared by sol-gel technique which relies on the chemical reaction of liquid precursors to form the glass. TEOS: H2O:C2H5OH:HNO3 in the molar ratio 1:5.5:3.5:0.1 was used in the preparation with HoCl3.6H2O as the Ho3+ source. Porous silica gel was obtained after stirring the mixture and ageing for few weeks. Annealing of the gel was done up to 1000°C to obtain densified glass samples with density 2.2 g/cm3 and refractive index 1.46. Absorption spectrum was recorded in the visible region which shows several peaks resulting from the transition from ground state 5I8 to various excited states. The hypersensitive transition 5I8→5G6 at 454 nm was observed to be particularly strong. This strong absorption in the blue-violet region gives the glass sample a pale-yellow appearance. Judd-Ofelt parameters were obtained from the absorption spectrum and used to study the optical properties of the prepared glass sample. Large value of the parameter Ω2 shows that the bonding of the dopant to the host network is more covalent than ionic. Photoluminescence spectrum was recorded in the visible region using 450 nm excitation which excites the Ho3+ ions to the 5G6 state. Luminescence peaks were observed at 490, 550, 662 and 756 nm resulting from the radiative relaxations from the 5F3 and 5S2 states to the lower energy states. Photoluminescence of considerable intensity was not observed in samples pre-annealing which is due to hydroxyl quenching caused by the residual hydroxyls from the starting materials for the preparation. Annealing was shown to significantly improve the luminescence which is attributed to the removal of residual hydroxyls.

Copyright

© 2018, the Authors. Published by Atlantis Press.

Open Access

This is an open access article distributed under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).

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TY  - CONF
AU  - Uzair Khan
AU  - Andrew L. Fanai
AU  - S. Rai
PY  - 2018/12
DA  - 2018/12
TI  - Optical properties of holmium-doped in sol-gel silica glass
BT  - Proceedings of the Mizoram Science Congress 2018 (MSC 2018) - Perspective and Trends in the Development of Science Education and Research
PB  - Atlantis Press
SP  - 194
EP  - 197
SN  - 2352-5401
UR  - https://doi.org/10.2991/msc-18.2018.33
DO  - 10.2991/msc-18.2018.33
ID  - Khan2018/12
ER  -