THERMAL BARRIER COATINGS THERMOMETRY BY FLUORESCENCE. Molly Gentleman, Matt Chambers, Samuel Margueron and David R. Clarke

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1 Groupe Français de Spectroscopie Vibrationnelle, 25, 26 et 27 JANVIER 2006, Spectroscopies Infrarouge et Raman «Mesures in situ et rayonnement thermique» THERMAL BARRIER COATINGS THERMOMETRY BY FLUORESCENCE Molly Gentleman, Matt Chambers, Samuel Margueron and David R. Clarke Materials Department, College of Engineering University of California, Santa Barbara, CA

2 Plan Thermal Barrier Coatings Fluorescence Thermometry of Eu:YSZ Current issues in calibrations: Effect of high energy excitation Effect of reabsorption and energy transfer

3 Thermal Barrier Coatings Thermal Barrier Coatings Moteur M88 (Snecma) Gradient 1 MK/m! 150 µm (ONERA)

4 YSZ: t -(ZrO 2-7wt% Y 2 O 3 ) Materials Engineering Materials Engineering Low conductivity, higher toughness Porous, columnar (EB-PVD) Optically Transparent (VIS-NIR) Extract from: CONCEPTS FOR LUMINESCENCE SENSING OF THERMAL BARRIER COATINGS, M. Gentleman and D. R. Clarke, HYPERCOAT NSF-EU PROGRAM Effects of radiative transfer, sintering, pollution, erosion

5 Fluorescence (Phosphorescence) Thermometry Interests : Remote sensing (In-Situ) «Independent» of optical path and gas emission Based on selective lifetime measurements General issues : Intensity at high temperature (thermal quenching) Remote collection system CMAS (pollutions infiltration) Others effect and noise (thermoluminescence, defects luminescence, impurities ) Doppler effect for measurements on mobile parts Feist J. P, Heyes A. L (2000) Europium-doped Yttria-stabilized Zirconia for High-temperature Phosphor Thermometry, Proceedings of the I MECH E Part L Journal of Materials: Design and Applications, Volume 214, Number 1: 7-12(6).

6 Rainbow Sensor & NDE Rainbow Sensor & NDE 5 D 0 -> 7 F 1 5 D 0 -> 7 F 2 Extract from: M. Gentleman and D. R. Clarke

7 Choice rare earth elements: Choice rare earth elements: Weakly coupled to the crystal field and lattice ( f orbital) Eu is a good candidate for high temperature Simplified Dieke Diagram of RE 3+

8 Lifetime measurements Lifetime measurements Optical set-up for calibration in temperature Laser (Q-switch) Nd:YAG (532 nm) 9 ns pulse (10Hz) fibre collection rod sample trigger Filters (+spectrometer) furnace PMT PC

9 Lifetime decay of Eu 5 D 0 -> 7 F 2 (606 nm) in YSZ Lifetime decay of Eu 5 D 0 -> 7 F 2 (606 nm) in YSZ (Log) Lifetime decay (spontaneous emission) Will be treated later

10 Lifetime decay of Eu 5 D 0 -> 7 F 2 (606 nm) in YSZ Lifetime decay of Eu 5 D 0 -> 7 F 2 (606 nm) in YSZ Constant Vacancy Concentration Increasing Stabilizer Concentration

11 Four levels model Four levels model 4 levels system supposing no temperature dependence of parameters N(n.r)/N(f) w ( n.r) =1/ γ*exp(- E / kt) = exp(- E/kT) 1/ τ = w Rad + w ( n.r) γ = s E= 1.54 ev

12 Multi-Phonon Scattering Model (up (up conversion) ( T 0K)[ ] p 1 / τ + n = w Rad + w p = n 1 [ exp ( hν / ) 1] 1 = kt n is the phonon occupancy factor v is the effective frequency of the accepting phonon mode p is the number of phonons needed to bridge the energy gap between the excited state and the ground state 1/W p (0K)=157 s hν= ev p= ev Discussion: Layne and al. (1977), Multiphonon relaxation of Rare-earth ions in oxide glasses, Phys. Rev. B, 16#1 pp10-21

13 Multi-Phonon Scattering Model Fitting parameters (unconstrained fit)

14 Current issues in calibrations Current issues in calibrations To get high intensity of luminescence of thin doping layers High energy density of laser excitation High concentration (Room temperature, Chromium doped alumina)

15 Effect of high energy density Effect of high energy density Glan-thomson polarizer Cr:Al2O3 Laser (532 nm) (pulse 9 ns) fibre Filters (spectrometer) Polarizer change laser density PMT

16 R-lines decays at different power densities R-lines decays at different power densities Increase of LASER density Al 2 O 3 (0.07wt%[Cr])

17 Multi-exponential transition spectroscopy (METS) Multi-exponential transition spectroscopy (METS) Log derivative di(t)/dln(t) 3 lifetime decays: Spontaneous emission Fast decay (induced transition?) Long decay (multiple electron excitation?) Gutierrez-Osuna, R., A. Gutierrez-Galvez, et al. (2003) Transient response analysis for temperature-modulated chemoresistors, Sensors and Actuators B 93:

18 Effect of concentration Effect of concentration Reabsorption laser luminescence Energy Transfer laser luminescence Cr Cr

19 Experimental set-up Experimental set-up Solid State Laser (26 mw*1ms)

20 Effect of reabsorption Effect of reabsorption Single crystal Objective magnification ~1 cm No objective An increase of optical path increases lifetime values

21 Effect of reabsorption Effect of reabsorption Polycrystalline alumina objx100 Lifetime depends on: Geometry of the set-up Concentration Thickness layer and porosity Reabsorption Coefficient in Temperature Difference of lifetime between 2 objective magnifications Include uncertainty on lifetime determination

22 Decay on highly doped alumina Decay on highly doped alumina Highly Cr doped alumina presents a non-exponential decay: Manifestation of time dependant Phenomenon: N(t) = Energy transfer : N 0 e -(t/ τ P(t) ) 1/ γ -(t/ τ ) N(t) = N e P(t)? 0 Very robust to use a stretch exponential decay: N(t) = N 0 e -(t/ τ ) 1/ γ

23 Conclusions Measurement where performed on Eu-YSZ up to 1100 C and is a good candidate for high temperature thermometry. We note that increase of energy of the laser increase fluorescence signal but others phenomenon occur. Lifetime measurement depends on: Geometry of the set-up Concentration, Temperature, Thickness layer and porosity Acknowledgements: University of California Santa Barbara, Office of Naval Research (MURI), HYPERCOAT, NSF-EU PROGRAM Bourse Lavoisier 2004 (Ministère des Affaires Etrangères)

24 Messages personnels Messages personnels Limoges SPCTS (2006 post-doc) Instrumentation du procédé d élaboration Frittage SHS par une caméra infrarouge rapide (ThermaCam SC3000) Spectro rapide (0.1-1 ms/barrette) vis-nir, ImSpector? Japon+UCSB ( ) Cutting edge project