1. October 16-20, 2011 – Columbus, Ohio
Effect of Ytterbium on Grain
Boundary Structure and
Grain Growth in Magnesium
Aluminate Spinel
George Ferko, Animesh Kundu,
Martin P. Harmer

2. Applications of Spinel
October 16-20, 2011 – Columbus, Ohio
Courtesy of TA&T
Courtesy of Armorline
• Armored windows
• Radomes
Desirable Properties
• Hardness
• Fracture toughness
• Transparency

3. LiF in Spinel
October 16-20, 2011 – Columbus, Ohio
Reimanis and Kleebe, J. Am. Ceram. Soc., 92 [7] (2009)

4. Spinel and Ytterbium
October 16-20, 2011 – Columbus, Ohio
Courtesy of JM Perkins and MH Lewis

5. Complexions
October 16-20, 2011 – Columbus, Ohio
S.J. Dillon et al. / Acta Materialia 55 (2007)

6. Experimental Procedure for
Bi-crystals
• Cleaning of single crystals
• Yb-doping (99.99% pure)
• Hot-pressing (1200ºC, ~4MPa,
1Hrs)
• Annealing (1600ºC, 2Hrs)
• Polishing
• FIB
• TEM
October 16-20, 2011 – Columbus, Ohio
Spinel (100)
Spinel (111)
Yb(NO3)3•xH2O

7. Experimental Procedure for
Pressureless Sintering
• Powder doping (500 ppm Yb)
• Uniaxial pressing (35 Mpa)
• CIPing (275 Mpa)
• Sintering (1800°C)
• Sectioning, grinding, and
polishing
• EBSD
October 16-20, 2011 – Columbus, Ohio
Baikowski S30CR
Powder Purity
S (ppm) 800-900
K(ppm) 40
Na(ppm) 11
Fe(ppm) <10
Ca(ppm) <10
Si(ppm) <10
Benameur et al., J. Am. Ceram. Soc. 94[5] (2011)

8. EBSD Data Processing
October 16-20, 2011 – Columbus, Ohio
Raw Data Grain Dilation Pore Data Removal
SEM Signal Overlay SEM Signal Grain Size Data

9. Identifying Abnormal Grains
October 16-20, 2011 – Columbus, Ohio
Grain Diameter (μm)
Frequency

10. Grain Growth
October 16-20, 2011 – Columbus, Ohio
500 ppm Yb-
doped
Undoped
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
3.5 3.7 3.9 4.1
log(Ḡ)(μm)
log(t) (s)

11. 1 Hour Sample Comparison
October 16-20, 2011 – Columbus, Ohio
Frequency
Grain Diameter (μm) Grain Diameter (μm)

12. 2 Hour Sample Comparison
October 16-20, 2011 – Columbus, Ohio
Frequency
Grain Diameter (μm) Grain Diameter (μm)

13. 4 Hour Sample Comparison
October 16-20, 2011 – Columbus, Ohio
Frequency
Grain Diameter (μm) Grain Diameter (μm)

14. October 16-20, 2011 – Columbus, Ohio
Grain Size Distribution
Comparison
Yb-doped Samples
1 Hour
2 Hour
4 Hour
Undoped Samples
1 Hour
2 Hour
4 Hour
Frequency
Grain Diameter (μm) Grain Diameter (μm)
Frequency

15. STEM of Bi-crystal
October 16-20, 2011 – Columbus, Ohio
Bright Field STEM Dark Field STEM
STEM work performed by Animesh Kundu

16. STEM of Bi-crystal
October 16-20, 2011 – Columbus, Ohio
Bright Field STEM Dark Field STEM
STEM work performed by Animesh Kundu

17. Future Work
October 16-20, 2011 – Columbus, Ohio
Hot-pressing (1200ºC, 60 Mpa)
Annealing (1400°C, 1600°C, 1800°C)
Polycrystals
Yb-doped Undoped
Grain Size Measurements (EBSD)
Density Measurements
Quantitative Analysis of Grain
Boundary Kinetics
Hot-pressing (1200ºC, 4 Mpa)
Annealing (1400°C, 1600°C, 1800°C)
Bi-crystals
Yb-doped
FIB Lift-out Method
HRTEM
HAADF STEM

18. Acknowledgements
• My advisor Prof. Martin P. Harmer
• Animesh Kundu for his unending assistance
• Funding provided by:
– NSF MERSEC (CMMI-1131408)
October 16-20, 2011 – Columbus, Ohio
Thank you!