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

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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

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0

50

100

150

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250

300

350

0 20 40 60 80 100

2 Theta (Degrees)

Inte

nsi

ty (

Co

un

ts)

Powder

Specimen 1

Specimen 5 XRD

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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

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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

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40

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0 20 40 60 80 100

2 Theta (Degrees)

Inte

nsi

ty (

Co

un

ts)

Sintered Pellet XRD Cont.

Specimen 10 XRD

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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