“Fluorophosphate glasses doped with Er3+ and Yb3+:
Structural and Photophysical Characterization”
Tuesday, May 12, 2015 11:00am-12:00pm
CREOL RM 103
Andrea S. S. de Camargo
Physics Institute of São Carlos, University of São Paulo,
São Carlos – SP, Brazil.
Celebrating the International Year of Light 2015
Abstract:
Rare-earth (RE)-doped oxide glasses and glass-ceramics are
still at the focus of much research for laser applications in the infrared and
visible spectral regions. In order to facilitate the development of materials
with optimized optical properties (high absorption and emission cross sections,
suitable excited state lifetime values, manageable energy transfer) while still
maintaining chemical and mechanical stability, detailed structural information
is of utmost importance. This information regards the chemical bonding
environment of the RE dopant, its coordination sphere, the distribution in the
amorphous (or partially crystalized) network and the possible formation of
clusters that can result in fluorescence quenching. The combination of optical
spectroscopic techniques (UV-VIS, FT-IR, steady-state and time resolved
fluorescence) with magnetic resonance techniques (NMR, EPR) offers the
opportunity to approach the systems from different points of view so that
structure-function correlations can be drawn. Among the most interesting
materials for current applications are phosphates glasses and ceramics. Still,
they present disadvantages such as low mechanical resistance and hygroscopicity
which can prevent laser action due to energy transfer to OH- groups. Lately,
oxyfluoride glasses have attracted much attention with the promise to combine
merits of fluorides (low phonon energy, moderate refractive indexes, and
extensive IR window) and of oxide glasses (high chemical and mechanical
stability and higher RE solubility). In this work, we present new
fluoro-aluminophosphate glasses with compositions
0.25BaF2–0.25SrF2–(0.3-x)Al(PO3)3–xAlF3–(0.2-z)YF3-zREF3 with x = 15 and 20
mol%, RE = Er3+ and/or Yb3+ (z =0.1, 0.25, 0.5, 1.0, 2.0 3.0 and 4.0 mol%). A
significant increase in lifetime values and fluorescence quantum efficiencies
is observed upon addition of fluorine and consecutive substitution of oxygen in
the first coordination sphere of RE, as confirmed by 19F NMR. The latter also
turns out to be very useful for quantifying fluoride losses during the
synthesis and differentiating between P- and Al-bonded fluorine species.
Furthermore, systematic compositional changes in the network structure have
been monitored by 31P, 27Al single resonance as well as 31P(19F), 31P(27Al),
27Al(19F), 27Al(31P) double resonance NMR leading to a comprehensive structural
description of the system. Besides the throughout characterization of
near-infrared emissions at 1.0 and 1.55 µm, the favorable energy transfer
between Yb3+ and Er3+ was also investigated in the visible (infrared to green
and red upconversion) ranges.
Biography:
Andrea de Camargo is a Bachelor (1996) and Master (1999) in
Chemistry and got her PhD degree in Applied Physics at the Physics Institute of
São Carlos, University of São Paulo, Brazil (2003). In 2006 she became
Assistant Professor of Physics at the same institute. From 2008-2011 she worked
at the Westfaelisches Wilhelms Universitaet Muenster in Germany, as an
Alexander von Humboldt Fellow and then CNPq Postdoctoral Fellow. Since her
return to São Carlos she has been working on the consolidation of her research
group dedicated to design, synthesis, spectroscopic investigations and
structural-functional correlations of luminescent and optical materials
(rare-earth doped glasses and glass ceramic for laser applications, mesoporous
silicates incorporated with highly luminescent molecular species, luminescent
nanoparticles, etc). She is one of the principal investigators of CeRTEV –
Center for Research, Technology and Education in Vitreous Materials, a joint
initiative to establish an Excellence Center in Glass Science and Technology in
São Carlos. In 2007 she was granted the prize L’OREAL for Women in Science,
Brazil, and subsequently the CNPq Research Productivity Fellowship, which she
still holds. In 2008 she became affiliated member of the Brazilian Academy of
Sciences. She has published over 50 papers and advised 3 PhDs and 4 MS thesis.
For additional information:
Dr. Leonid B. Glebov
407-823-6983
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