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28. 1 D 2. 26. 24. 22. 1 G 4. 20. 650nm. 18. 476nm. 16. 3 F 2,3. 14. Energy (1000cm -1 ). 3 H 4. 12. 10. 3 H 5. 8. 3 F 4. 6. 4. 790nm. 2. 3 H 6. 0. 10%Zr/1% Nd. 7.5%Zr/1% Er. 10%Zr/1% Ho. 1% Europium Glass Under UV light. partial energy diagram for Eu 3+. x10 3 cm -1. - PowerPoint PPT Presentation
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Fluorescence of Rare Earth Ions in Binary Zirconia-Silica Sol-Fluorescence of Rare Earth Ions in Binary Zirconia-Silica Sol-Gel GlassesGel Glasses
Jessica R. Callahan, Karen S. Brewer, Ann J. SilversmithDepartments of Chemistry and Physics
Hamilton College, Clinton, NY
Mix 4.90 mL TMOS with 2.5 mL ethanol; stir for 10 minutes
Add 0.50 mL deionized H2O and 20 µL conc. HCl; stir for 90 min
Stir 10 minutes or until all light precipitate has dissolved; cast into 12
75 mm tightly capped polypropylene test tubes
Add solution of 1% RE ions dissolved in
2.5 mL H2O
… Zr(OPr)4 via syringe, stir 10
minutes
Add 2.5 mL ethanol
simultaneously with…
Often using two stir bars was helpful
5D0
partial energy diagram for Eu3+
0
5
10
15
20
25
x103cm-1
Ener
gy
7F0
7F27F1
5D1
5D2
5D3QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
synthesis and processingsynthesis and processing
sample qualitysample quality optically clear were monoliths obtained
for zirconia content from 2% to 30% some cracking can occur during drying
if water and solvent evaporated too quickly
annealing above 750 ˚C can cause phase separation of the zirconia, producing opaque glassy materials
spectroscopic resultsspectroscopic results
referencesreferences
acknowledgementsacknowledgementsThis work sponsored in part by the
Research Corporation through a Cottrell College Science Award
JRC thanks the General Electric Fund at Hamilton College for summer research stipends
sol-gel glass vs. melt glasssol-gel glass vs. melt glassAdvantages3
high purity starting materials & lower processing temperatures
higher concentrations of RE3+ possible simple manipulations & greater homogeneity of samples chemical composition can be varied & precisely controlled processing parameters can be readily changed & optimized
Disadvantages3
heating must be carefully & consistently controlled processing times can be long (> 2 weeks) cracking during aging, drying, or densification can be
extensive residual hydroxyl groups & RE clustering in samples
quench fluorescence
introductionintroductionOur success in the synthesis of rare earth-doped TiO2-SiO2 glasses and their spectroscopic results1 led us to re-examine our preliminary work on the synthesis of the zirconium analogs.In this project, rare earth-doped zirconia-silica glasses have been successfully produced through the co-hydrolysis of Zr(O iPr)4 with Si(OMe)4 in ethanol. Careful drying and aging of the gels produced clear, crack-free glass monoliths. Optical properties were then studied via laser and fluorescence spectroscopy.Synthetic obstacles rapid hydrolysis of the zirconium alkoxide precursor vs. that of
TMOS precipitation of the zirconia as a opaque solid during synthesis choosing processing temperatures & programs to limit the
precipitation of zirconia during transformation from gel to glass
why dope glasses with rare earth ions?why dope glasses with rare earth ions?In the lanthanide series, the optically active electrons are shielded by filled s and p shells producing
narrow spectral lines long fluorescence lifetimes energy levels that are insensitive to the environment
Applications of rare earth-doped materials2
phosphors solid state lasers optical fibers waveguides antireflective coatings
project goalsproject goalsSynthesize glasses doped with Eu3+ and other rare earth
cations including erbium, neodymium, holmium, and thuliumOptimize processing parameters to obtain clear, crack-free
glass monoliths Match concentrations of Zr with Ti glasses for direct
spectroscopic comparisonIncrease the percentage of zirconium in the glass samples (up
to 30% vs. SiO2)Compare optical properties of the zirconia-silica glasses with
other sol-gel glasses (e.g., silica, titiania-silica, and chelated rare earth dried gels)
challenges in doping sol-gel glasses with rare earth ionschallenges in doping sol-gel glasses with rare earth ionsClustering of the rare earth cations in the glass4
only a limited number of non-network oxygen atoms for the RE3+ to bond within the glass
clusters formed through RE-O-RE bonding in the glass matrix energy migration is facilitated in the clusters fluorescence is quenched through a cross relaxation mechanism
Residual hydroxyl (OH) groups5
present even after annealing to high temperatures give reduced fluorescence lifetimes through a non-radiative decay mechanism
when close to the rare earth cation in the glass
excitation spectrum of Eu-doped zirconia-silica glass
250 350 450 550wavelength (nm)
fluorescence (arb. units)
fluorescence occurs from the 5D0 level in Eu3+
sample excited in the charge-transfer region Al co-doped sample must be annealed at 1000˚C before significant fluorescence
is observed Zr co-doped glass annealed only to 750 ˚C and gave comparable fluorescence in general, the Zr co-doped glasses fluoresce more brightly than Al co-doped &
about the same as Ti co-doped
europium in zirconia-silica glass annealed at 750 ˚C has a longer decay time (~1.4 ms) compared to aluminum co-doped silica glass annealed to 1000 ˚C
glasses without co-dopants have very short lifetimes
different spectral profiles when excitation is changed
little energy migration between the different RE3+ sites in the glass
shows declustering of the Eu3+ in the glass similar to results in Al co-doping Ti results show enhanced peak at 613 nm
with longer exc indicating reduced energy migration and more uniform site distribution
note that Tm/Al fluorescence spectrum is multiplied by 5 in the above spectrum
Zr co-doped glass fluoresces more efficiently than Al co-doped & about the same as Ti co-doped
closely spaced energy levels prevents efficient luminescence
here, however, in glass annealed at 750 ˚C, we observe fairly strong fluorescence
monitored at 612 nm strongest excitation occurs at 393
nm corresponding to the 7F05D3 excitation
(1) Boye, D.M.; Silversmith, A.J.; Nolen, J.; Rumney, L.; Shaye, D.; Smith, B.C.; Brewer, K.S. J. Lumin. 2001, 94-95, 279. Silversmith, A.J.; Boye, D.M.; Anderman, R.E.; Brewer, K.S. J. Lumin. 2001, 94-95, 275.
(2) Steckl, A.J.; Zavada, J.M., eds. MRS Bulletin, 1999, 24, 16-56.Scheps, R. Prog. Quantum Electron. 1996, 20, 271.Reisfeld, R. Opt. Mater. 2001, 16, 1.Weber, M.J. J. Non-Cryst. Solids, 1990, 123, 208.
(3) Brinker, C.J.; Scherer, G.W. Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing, Academic Press, Boston, 1990.
(4) Almeida, R.M. et al. J. Non-Cryst. Solids 1998, 232-234, 65.Arai, K.; Namikawa, H.; Kumata, K.; Honda, T.; Ishii, Y.; Handa, T. J. Appl. Phys. 1986, 59, 3430.
(5) Lochhead, M.J.; Bray, K.L. Chem. Mater. 1995, 7, 572.Stone, B.T.; Costa, V.C.; Bray, K.L. Chem. Mater. 1997, 9, 2592.Nogami, M. J. Non-Cryst. Solids 1999, 259, 170.
partial energy diagram for Ho3+
5
10
15
20
25
x103cm-1
Ener
gy
5I8
5F5
5G4
3K85S2
compare to our previous work in Al and Ti co-doped silica glasses1
fluorescence of holmium-doped zirconia-silica glass
520 570 620 670wavelength (nm)
fluorescence (arb. units)
10% Zr, 12h dwell at 750 ˚Cexcite 457 nm
emission spectrum comparing Eu-doped glasses
570 590 610 630wavelength (nm)
fluorescence (arb. units)
exc 254nm, RT 2%Al 1%Eu
25% Zr
5D0→7F0
5D0→7F1
5D0→7F2
addition of 1% RE3+ is the critical step high Zr amounts often gelled upon
contact with the RE3+(aq) solution after cast into tubes, sols were gelled at
40 ˚C (24 h), 60 ˚C (24 h) and 80 ˚C (48 h) before processing in furnace
dried gels heated from ambient temperature to 750 ˚C over a period of 72 h
heating rate = 1 ˚C/min to preserve integrity of sample
dwell temperatures = 250 and 500 ˚C to remove organics and residual water/OH groups
Homogeneous sol Reaction
hydrolysis and condensation,ambient conditions,pH 1.5 to 3.5
Gelationpolymeric gel forms “wet” gel
2 days, 40°C
Agingsolvents escape,pore contraction
1-3 days, 60°C
Dryingshrinkage,densification,pore collapse,
2-4 days, 80°C
europium fluorescenceeuropium fluorescence
enhanced fluorescence in thulium and holmiumenhanced fluorescence in thulium and holmium
02468
10121416182022242628
Ener
gy (1
000c
m-
1 )
3H6
3F4
1G4
1D2
650n
m
476n
m
3H5
3H4
3F2,3
790n
m
partial energy diagram for Tm3+
partial energy diagram for Ho3+
Pr Nd
Er Eu
550
nm
663
nm
our collaboratorsour collaborators
Ann SilversmithHamilton College
Physics
Dan BoyeDavidson CollegePhysics
Ken KrebsFranklin & Marshall
CollegePhysics
Karen BrewerHamilton College
Chemistry
comparison of Tm-doped glasses
600 650 700 750 800wavelength (nm)
intensity (arbitrary units)
Tm/Al glass 750˚C x5
Tm/10%Zr, 750˚C for 12 hrs
476 nm exc
comparison of fluorescence lifetimes
0 1 2 3 4 5 6time (ms)
ln(fluorescence)
25%Zr
Al co-dopeno co-dope
temperature program for zirconia-silica glasses
0100200300400500600700800
0 1 2 3 4time (days)
temperature (˚C)
fluorescence line narrowing results
590 600 610 620 630 640 650wavelength (nm)
intensity (arbitrary units)
577nm
581nm
579.5nm10%Zr/1% Ho7.5%Zr/1% Er10%Zr/1% Nd
1% Thulium Glass
7.5%Zr 10%Zr 12.5%Zr
20%Zr
1% Europium Glass Under UV light
2%Zr 12.5%Zr 20%Zr 30%Zr
579.5 nm573.2 nm
600 610 620 630 640
575.1nm
581.6nm
575nm
577nm578nm
579nm
wavelength (nm)
SiO2 glass Al3+ co-doped
SiO2 glass Ti4+ co-doped
SiO2 glass no co-dopants