Groupe Français de Spectroscopie Vibrationnelle, 25, 26 et 27 JANVIER 2006,Spectroscopies Infrarouge et Raman« Mesures in situ et rayonnement thermique »

THERMAL BARRIER COATINGSTHERMOMETRY BY FLUORESCENCE

THERMAL BARRIER COATINGSTHERMOMETRY BY FLUORESCENCE

Molly Gentleman, Matt Chambers, Samuel Margueron and David R. Clarke

Materials Department, College of EngineeringUniversity of California, Santa Barbara,

CA 93106-5050

PlanPlan

Thermal Barrier Coatings

Fluorescence Thermometry of Eu:YSZ

Current issues in calibrations:– Effect of high energy excitation– Effect of reabsorption and energy transfer

Thermal Barrier CoatingsThermal Barrier Coatings

Moteur M88(Snecma)

150 µm

(ONERA)

Gradient 1 MK/m!

Materials EngineeringMaterials Engineering

YSZ: t’-(ZrO2 -7wt% Y2O3)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

Fluorescence (Phosphorescence) Thermometry

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 systemCMAS (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 Zirconiafor High-temperature Phosphor Thermometry”, Proceedings of the I MECH EPart L Journal of Materials: Design and Applications, Volume 214, Number 1: 7-12(6).

Rainbow Sensor & NDERainbow Sensor & NDE

5D0->7F1 5D0->7F2

Extract from: M. Gentleman and D. R. Clarke

Choice rare earth elements:Choice rare earth elements:

Weakly coupled tothe crystal field andlattice (‘f’ orbital)

Eu is a good candidate for hightemperature

Simplified Dieke Diagram of RE3+

Lifetime measurementsLifetime measurements

Optical set-up for calibration in temperature

Laser (Q-switch)Nd:YAG (532 nm)

furnaceFilters (+spectrometer)

PMT

PC

collection rodfibre

sample9 ns pulse (10Hz)

trigger

Lifetime decay of Eu 5D0-> 7F2 (606 nm) in YSZLifetime decay of Eu 5D0-> 7F2 (606 nm) in YSZ

Lifetimedecay

(Log)

(spontaneous emission)

Will be treated later

Lifetime decay of Eu 5D0-> 7F2 (606 nm) in YSZLifetime decay of Eu 5D0-> 7F2 (606 nm) in YSZ

Constant Vacancy Concentration

IncreasingStabilizerConcentration

Four levels modelFour levels model

( )( ) kT)/E(-expγ*/1=w

ww/1r.n

r.nRad

∆+=τ4 levels system supposing no temperature

dependence of parameters E/kT)(-exp)N(n.r)/N(f ∆=

γ = 2.4 10-13 s ∆E= 1.54 eV

Multi-Phonon Scattering Model(up conversion)

Multi-Phonon Scattering Model(up conversion)

( ) [ ]pK0TpRad 1nww/1 ++= =τ

( )[ ] 11/exp −−= kThn ν

n is the phonon occupancy factorv is the effective frequency of the

accepting phonon modep is the number of phonons needed to

bridge the energy gap between the excited state and the ground state

1/Wp(0K)=157 shν=0.0631 eVp=24.47 1.54 eV

Discussion: Layne and al. (1977), Multiphonon relaxation ofRare-earth ions in oxide glasses, Phys. Rev. B, 16#1 pp10-21

Multi-Phonon Scattering ModelFitting parameters

Multi-Phonon Scattering ModelFitting parameters

(unconstrained fit)

Current issues in calibrationsCurrent 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)

Effect of high energy densityEffect of high energy density

Glan-thomsonpolarizer

Cr:Al2O3

Laser (532 nm)(pulse 9 ns)

Filters (spectrometer)

fibre

Polarizer changelaser density PMT

R-lines decays at different power densitiesR-lines decays at different power densities

Al2O3(0.07wt%[Cr])

Increase of LASERdensity

Multi-exponential transition spectroscopy (METS)Multi-exponential transition spectroscopy (METS)

Log derivative dI(t)/dln(t)

3 lifetime decays:

Spontaneous emissionFast 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: 57-66.

Effect of concentrationEffect of concentration

laser

luminescence

Cr

laser

Reabsorption

Energy Transfer Cr

luminescence

Experimental set-upExperimental set-up

Solid State Laser (26 mW*1ms)

Effect of reabsorptionEffect of reabsorption

Single crystal

Objective magnification

~1 cm

No objective

An increase of optical path increases lifetime values

Effect of reabsorptionEffect of reabsorption

Polycrystalline alumina

Difference of lifetime between 2 objective magnifications

objx100

Lifetime depends on:

Geometry of the set-upConcentrationThickness layer and

porosityReabsorption Coefficient in

Temperature

Include uncertainty on lifetime determination

Decay on highly doped aluminaDecay on highly doped alumina

Highly Cr doped alumina presents a non-exponential decay: Manifestation of time dependant

Phenomenon:

Energy transfer :

eNN(t) )-(t/0

)t(P−= τ

eNN(t)1/)-(t/

0

γτ= P(t) ?

eNN(t)1/)-(t/

0

γτ=Very robust to use a stretch exponential decay:

ConclusionsConclusions

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 PROGRAMBourse ‘Lavoisier’ 2004 (Ministère des Affaires Etrangères)

Messages personnelsMessages 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 (2007-2010)– Cutting edge project…