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SENIOR DESIGN PROGRESS REPORT
Sintering and Optical Properties of TransparentLu2Hf2O7 Scintillators
Student Name: Kyle Crosby Harrison Deamon
Mark Minchello
Academic Advisor: Leon Shaw University of Connecticut (UConn)
Industry Advisor: Edgar Van Loef Radiation Monitoring Devices (RMD)
November 10, 2006
Objectives
Create a transparent ceramic from Lu2Hf2O7
powder Transparency results when solid is 99.99% of the
theoretical density (no pores to deflect phonons) Theoretical density of Lu2Hf2O7 = 9.95 g/mL
Confirm ideal cold pressing, sintering, and hot isostatic pressing (HIP) conditions
If successful, these ceramics will be doped with Ce and used as scintillators.
Ceramic Scintillators
Definition Emits light when excited by radiation
Transparency Allows photons to escape
Stopping efficiency Attenuation directly related to density
Doping Intermediate energy level for e- excitation
Phase Diagram
HfO2 – Lu2O3
Composition of powder
Uniaxial Press
Pellets at 450 MPa Non-uniform densification
Lamellar cracking
Pressed at 50 & 150 MPa w/ ethanol lubricant Improved handling No lamellar cracking
.5” die
Sintering Mechanisms
• Particles after pressing
•Point contact
• Pore formation and particle coalescence
•Neck growth
•Density < 70%
•Pore reduction
•Densification with closed spherical pores
•Density > 92%
Graphite Furnace
Sinter temperatures 1600°C, 1700°C, 1800°C, 1900°C, 2100°C
Sinter cycle schedule 0 - 1000 °C 45 minutes 1000 - 1800 °C 10°/minute 1800 °C 120 minute soak 1800 - 1000 °C 20°/minute 1000 - 0 °C free cooling
Furnace Atmosphere
Helium Smallest inert gas
Argon Larger atomic radius
Sintering Difficulties
Furnace repair Filament replacement
Reduction Loss of O2
Oxidation Furnace
Optimal conditions 1400 °C 2 hour dwell
Necessary procedure Reintroduced O2
Characterization
XRD Continuous spectrum analysis d-spacing to determine lattice parameter
Optical Microscopy Microstructure examination Relative degree of porosity, relative pore size
SEM Powder particle size distribution Sintering effects
X-Ray Diffraction (XRD)
Bruker D5005 2.2 kW copper x-ray
tubes
Operation parameters 40 kV & 40mA 10°-90° scan, .02 step size, 4° per minute
Powder Diffraction Pattern
Lu2Hf2O7 Powder XRD
-50
0
50
100
150
200
250
300
350
0 20 40 60 80 100
2 Theta (Degrees)
Inte
ns
ity
(C
ou
nts
)
Specimen 1 XRD
-20
0
20
40
60
80
100
120
140
0 20 40 60 80 100
2 Theta (Degrees)
Inte
ns
ity
(C
ou
nts
)Sintered Pellet Diffraction Pattern
Powder/Sintered Pellet Comparison
Powder/Sintered Pellet Comparison
-50
0
50
100
150
200
250
300
350
0 20 40 60 80 100
2 Theta (Degrees)
Inte
nsi
ty (
Co
un
ts)
Powder
Specimen 1
Specimen 5 XRD
-20
0
20
40
60
80
100
120
140
0 20 40 60 80 100
2 Theta (Degrees)
Inte
nsity
(Cou
nts)
Oxidized Pellet Diffraction Pattern
Powder/Sintered Pellet/Oxidized Pellet Comparison
Powder/Sintered Pellet/Oxidized Pellet Comparison
-50
0
50
100
150
200
250
300
350
0 20 40 60 80 100
2 Theta (Degrees)
Inte
nsi
ty (
Co
un
ts)
Powder
Specimen 1
Specimen 5
Sintered Pellet XRD Cont.
Speicmen 9
-20
0
20
40
60
80
100
120
140
0 20 40 60 80 100
2 Theta (Degrees)
Inte
nsi
ty (
Co
un
ts)
Sintered Pellet XRD Cont.
Specimen 10 XRD
-20
0
20
40
60
80
100
120
140
160
0 20 40 60 80 100
2 Theta (Degrees)
Inte
ns
ity
(C
ou
nts
)
XRD Analysis of Lattice Parameter
ao observed versus ao given by Brixner
Using Bragg’s Law of Diffraction Peaks occur at 2θB
nλ = 2dsinθB
d = ao/(√h2+k2+l2)
Lu2Hf2O7 Powder XRD
0
50
100
150
200
250
300
350
0 20 40 60 80 100
2 Theta (Degrees)
Inte
ns
ity
(C
ou
nts
)
2θB
Lattice Parameter CalculationsPowder XRD
Peak # 2θ (°) θ (°) λ (Å) Cu d (Å) hkl a, obs. a from Brixner % error
1 30.1 15.05 1.542 2.97 222 10.2884 10.2998 0.110682
2 35 17.5 1.542 2.564 400 10.256 10.2998 0.425251
3 50.2 25.1 1.542 1.818 440 10.2842 10.2998 0.151459
4 59.8 29.9 1.542 1.547 622 10.2616 10.2998 0.370881
5 62.6 31.3 1.542 1.484 444 10.2815 10.2998 0.177673
Specimen 1 XRD, Sintered not oxidized
Peak # 2θ (°) θ (°) λ (Å) Cu d (Å) hkl a, obs. a from Brixner % error
1 30 15 1.542 2.979 222 10.32 10.2998 -0.19612
2 35.1 17.55 1.542 2.557 400 10.228 10.2998 0.697101
3 50 25 1.542 1.824 440 10.318 10.2998 -0.1767
4 59.5 29.75 1.542 1.554 622 10.308 10.2998 -0.07961
5 62.5 31.25 1.542 1.486 444 10.295 10.2998 0.046603
Specimen 5 XRD, Sintered and Oxidized
Peak # 2θ (°) θ (°) λ (Å) Cu d (Å) hkl a, obs. a from Brixner % error
1 30.1 15.05 1.542 2.969 222 10.285 10.2998 0.143692
2 34.9 17.45 1.542 2.571 400 10.284 10.2998 0.153401
3 50.05 25.025 1.542 1.823 440 10.312 10.2998 -0.11845
4 59.5 29.75 1.542 1.554 622 10.308 10.2998 -0.07961
5 63.6 31.8 1.542 1.463 444 10.136 10.2998 1.590322
Optical Microscopy
Nikon inverted light
1700°C 1800°C 1900°C
2100°C 2100°C-HIP
Optical Microscopy – 10x Mag - 50μm markers
1700°C
2100°C
1900°C
2100°C-HIP
1800°C
Optical Microscopy – 20x Mag - 20μm markers
Crack propagation shows sufficient density
Images of 1900°C sintered specimen
Microhardness Testing
Electron Microscopy
AMRay 1000A SEM 40 kV accelerating potential 15 mA filament current Secondary electron detection mode
Electron Microscopy
Although the depth of field and resolution are better, the desired data is much easier and quicker to obtain with optical microscopy No need to make the sample conductive
through sputter coating No need to wait for the column to come down to
vacuum
Particle Size Analysis
RMD: Trans-Tech data
Avg. size = 1.181 μm
Powder particles at 2200x mag. Red bar is 1.06 microns.
Powder Particle Measurement
Sintered pellet at 795x mag. Red bar is 6.36 microns.
Sintered Particle Measurement
Sintering Effects
Particle coalescence Average particle diameter increase
Avg. sintered particle size = 5.691 μm
vs.
Avg. powder particle size = 1.055 μm
Sample #
Axial Pres
s.
Ethanol ρ Bef. S.
% of Theor
. Sinter Cycleρ After
S.
% of Theor. HIP Cycle
Density A.H. % of Theor.
(Mpa) (g/cm3) (g/cm3)
1 50 No 3.66 36.8
2 50 Yes 3.64 36.6
3 50 No 3.66 36.8
4 150 Yes 5.39 54.2 2 h. 1600C 9.06 91.1
5 50 No 3.66 36.8 2 h. 1700C 9.8 98.5
6 150 Yes 5.39 54.2 2 h. 1700C 9.78 98.3
7 50 No 3.66 36.8 2 h. 1800C 9.55 96.0
8 150 Yes 5.39 54.2 0.0
9 150 Yes 5.39 54.2 2 h. 1900C 8.07 81.1
10 150 Yes 5.39 54.2 1 h. 19C,21C 9.81 98.6
11 150 Yes 5.39 54.2 0.0
12 150 Yes 5.39 54.2 1 h. 19C,21C 9.81 98.6
13 150 Yes 5.39 54.2 1 h. 19C,21C 9.81 98.6 21 ksi,2100C 9.85 99.0
Specimen Database
Effects of Sintering on Density
Sintering Temperature Vs. Density
7.58
8.59
9.510
10.5
1500 1700 1900 2100 2300
Temperature (C)
Den
sity
(g/
cm3 )
Actual
Theoretical
Project Impact
Societal Radiation detection
Economic Cheaper than high quality crystal processing
Environmental No effects apparent to date
Alternative Solutions
CIP Increased pressure More uniform green density
Crucible atmosphere Hole in crucible cover Purge with He
HIP Continued cycle development
HIP
Limitations of AIP6-30H 2200 °C maximum 30,000 psi limit
Time constraints Unit was not operational
until 4/24/07
Project Timeline
Senior Design - Sintering and Optical Properties of Transparent Lu2Hf2O7 Scintillators
Aug Sept Oct Nov Dec Jan Feb Mar Apr May
Initial Meeting
Topic Research
Proposal - Draft 29-Sep
Proposal - Final 2-Nov
Proposal Presentation 10-Nov
Acquire Materials
Testing
Progress Report - Draft
Progress Report - Final 9-Feb
Progress Presentation 2-Feb
Final Report - Draft
Final Report - Final 4-May
Final Presentation 27-Apr
References
Anderson, Kelvin. Product Control Evaluation Sheet. Trans-Tech. Adamstown. 2006.
Brixner, L.H. Structural and Luminescent Properties of the Ln2Hf2O7-type Rare Earth Elements. Experimental Station. Wilmington. 1984.
Callister, William D. Jr. Materials Science and Engineering An Introduction. John Wiley & Son Inc. 2003.
http://en.wikipedia.org