1. Novel phosphate glass-ceramics and particles-containing phosphate glasses
Laeticia Petit,
Laboratory of Photonics
Tampere University of Technology
Finland
Acknowledgement
Academy of Finland (Academy Project ).

2. Tampere University of Technology
Tampere, the third largest city in Finland (220,000 inhabitants)
TUT was established in 1965.
Approx. 1,700 employees and 8,300 students (2015)
Glasses for Photonics group in the Photonics Laboratory (formerly ORC merged in Jan with the optics team of the physics department)

3. New glass-based materials with improved spectroscopic properties
Different approaches to control the site of the rare-earth
Change the glass composition
Particles-containing glass obtained by doping directly the glass with the nanoparticles
GC obtained by heat treating the glass leading to in-situ particles growth in glass
Schematic diagram of RE distribution in various glasses*
Glass
Particles-containing glass
Glass-ceramic (GC)
*J. Zhao et al, Adv. Optical Mater. 2016, doi:  /adom

4. Er doped glasses and glass-ceramics
Glasses composition (mol%):
(75 NaPO3-(25-x) CaO-xCaF2) doped with 0.15mol% Er2O3
with x ranging from 0 to 25
Rare-Earth doped oxyfluoride phosphate glasses
Understand impact of the glass composition on the spectroscopic properties of the glasses
Rare-Earth doped glass-ceramics
Check if crystals forming in the glass-ceramics are Er3+ doped.
Standard melting process in air, Tmelt=900oC for 5min
From previous work, 10at% of F expected to evaporate during the melting

5. Some properties of the as-prepared glasses
IR spectra
Absorption spectra
Increase in x
Shift of the bands, increase in intensity of the bands at 700, and 1240cm-1 and decrease in intensity of the band at 880 cm-1
Shift of the band gap to lower wavelength
No variation in sabs at 980nm and 1.5µm
Increase in Q2 tetrahedra at the expense of Q1 units with the formation of P-F bonds

6. No noticeable changes in the shape of the emission
IR emission properties
Normalized emission spectra Relative intensity of the emission at 1530nm
(lexc=976nm)
Increase in x
No noticeable changes in the shape of the emission
Decrease in the intensity of the emission at 1.5µm due to the low phonon energy of CaF2
Site of the Er3+ ions not strongly modified by the change in the glass composition

7. Visible emission properties
Upconversion spectra Normalized upconversion spectra
(lexc=976nm)
Increase in x
Increase in intensity of the visible emission bands due to low phonon energy
Increase in red emission compared to green emission due to increase in Er3+:4I13/2 level lifetime from 2.9 to 6.9ms (x from 0 to 25)

8. Post heat treatment (nucleation and growth):
Glass-ceramic method
Post heat treatment (nucleation and growth):
Tg+20°C for 17 h
Tp from 15 min to 1 h
An increase in the CaF2 content in Er3+ doped glasses
→ ↓ the crystallization

9. XRD analysis Ca2P2O7 main phase found in glasses with x<20
XRD pattern of the glasses after 1h at Tp
Ca2P2O7 main phase found in glasses with x<20
Na2Ca2(P2O7)F2 suspected in glasses with x=10 and 20
CaF2 found in the glass with x=25

10. SEM Surface to bulk crystallization when x increases to 25mol%
(as seen in undoped glasses)

11. IR emission properties
Normalized emission spectra prior to and after heat treatment of
x= x=25
(lexc=976nm)
After heat treatment
Visible changes in the shape of the emission ONLY from the glass x=0
Slight reduction in intensity of emission for the glass with x=0 probably due to reduction in Er-Er distance
No change in the intensity of emission of the glasses >0

12. Normalized upconversion spectra
Visible emission properties
Upconversion spectra
of the glass with x=0
Normalized upconversion spectra
of the glass with x=25
(lexc=976nm)
After heat treatment
Increase in intensity of the upconversion
→ Er3+ ions suspected to be embedded in crystals
Upconversion detected only for the glass with x=25 & Decrease in the red emission compared to green for glass with x=25
→ Er3+ ions suspected to remain in the glass

13. Modified melting process
Direct particles doping method
Glass matrix: 50P2O5-10Na2O-40SrO (mol%)
Modified melting process
Melting
10 min at 1050°C
Addition of the MPs
Doping T< 1050oC
Annealing
4 h at 400 oC
Quenching after
x min (dwell time)
Furnace
Quartz
crucible
As-quenched glass
standard raw materials
To balance the survival and dispersion of the MPs 2 parameters to optimize:
doping temperature
dwell time before quenching the glass
Composition of the microparticles (MPs): SrAl2O4:Eu2+,Dy3+ microparticles from Jinan G.L. New Materials, China, BG-01

14. Optimization of the direct doping process
Temperature
975oC oC oC
Analysis of the images using ImageJ, Java-based image processing program
3min
5min
Glass with more uniform PL = SdtDev as small as possible
Based on ImageJ analysis and on the luminescence properties of the glasses
Optimized doping temperature = 1000oC
Optimized dwell time= 5min
10min

15. Particles containing glasses
Glass matrix: 50P2O5-10Na2O-40SrO (mol%) Particles: Er: Al2O3, Er:TiO2, Er,Yb:YAG (Y3Al5O12) YAG NPs also prepared with a layer of silica with a thickness of 5 (YAG5) and 25nm (YAG25) All particles are thermally stable at 1000oC, the doping temperature
SEM image of Er:TiO2
TEM image of YAG5
20nm

16. Er: Al2O3 & Er:TiO2 containing glasses
Normalized emission spectra
(lexc=976nm)
Picture of prepared glasses along with the weight-% of added NPs
Emission band of the NPs is different after being added in the glass
→ Er3+ in amorphous network
in agreement with the increase in the Er3+:4I13/2 lifetime after adding the NPs in the glasses

17. YAG-containing glasses
1.25w% of YAG =
0.0038mol%Er2O3 – 0.035mol%Yb2O3
Picture of YAG-containing glasses (1.25wgt% of YAG)
with 5nm silica layer
with 25nm silica layer
Upconversion spectra (lexc=980nm)
Agglomerates from the drying of the YAG-containing solutions.
Successful preparation of phosphate glasses with upconversion
while using small amount of RE
Stronger upconversion from YAG0-containing glasses

18. YAG-containing glasses
Composition analysis along the line
(mol% in oxide)
SEM picture of an agglomerate found in YAG0-containing glass
Composition of the glass in accordance with the theoretical one
Sr-rich crystals seen around the particles
Al2O3 and Y2O3 detected
(SiO2 in the YAG5 and YAG25 containing glasses)
A toi de mettre en forme
From the upconversion measurement and the composition analysis,
no doubt about the survival of the YAG NPs
BUT with a different crystalline phase.

19. Conclusion
Always try to control the site of the RE to tailor the spectroscopic properties of the glass
Maybe possible using the glass-ceramic method BUT the heat treatment of glass does not necessarily lead to the in-situ volume precipitation of Er3+ containing crystals
Successful preparation of upconverter phosphate glasses using direct particles doping method
Challenges between the dispersion and survival of the particles which are correlated to corrosion of particles in the glass melt

20. Collaboration
Prof. Jonathan Massera and Dr. Mikko Hokka – TUT (Finland)
Dr. Mika Lastusaari – Turku University (Finland)
Prof. Daniel Milanese - Politecnico di Torino (Italy)
Prof. Bruno Bureau – Rennes University (France)
Dr. Thierry Cardinal and Dr. Benoit Glorieux – Bordeaux University (France)
Prof. Delia Brauer – Jena University (Germany)
Dr. Dan Sporea - Center for Advanced Laser Technologies (Romania)
Prof. John Ballato – Clemson University (SC, USA)