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Materials Physics Department

Josh Sugar

ACSTEM text
Principal Member of the Technical Staff
Materials Physics Department
Sandia National Laboratories
Livermore, CA 94550
925-294-1344 / jdsugar@sandia.gov

 

Research Summary
My research aim is to understand how to control the formation and evolution of microstructural features in materials. Using advanced quantitative electron microscopy techniques, I study the mechanisms responsible for the formation of microstructural features during materials synthesis and the evolution of features while in service. The features of interest can range in size from atomic dimensions to hundreds of microns in scale. Ultimately, the goal of my research is to explain the relationship between these microstructural features and materials performance. My ongoing research projects include:

I have expertise in the area of quantitative electron microscopy and use a number of advanced techniques that include:

 

Research Highlights

Battery Degradation:
We used Scanning Transmission X-Ray Microscopy (STXM) and Energy-Filtered TEM (EFTEM) to study the Li intercalation reaction in LiFePO4. We found that nucleation of new phases in this material is a critical rate-limiting step during battery charge/discharge.

References:
1. Chueh, W.C., F. El Gabaly, J.D. Sugar, N.C. Bartelt, A.H. McDaniel, K.R. Fenton, K.R. Zavadil, T. Tyliszczak, W. Lai, and K.F. McCarty, Intercalation Pathway in Many-Particle LiFePO4 Electrode Revealed by Nanoscale State-of-Charge Mapping. Nano Lett, 2013. 13(3): p. 866-72.
2. Sugar, J.D., F. El Gabaly, W.C. Chueh, K.R. Fenton, T. Tyliszczak, P.G. Kotula, and N.C. Bartelt, High-resolution chemical analysis on cycled LiFePO4 battery electrodes using energy-filtered transmission electron microscopy. Journal of Power Sources, 2014. 246(0): p. 512-521.

Macintosh HD:Users:jdsugar:Documents:Papers:EFTEM Li:Figure7.png
A comparison of Fe state of charge mapping with STXM and EFTEM. There is good agreement between the two techniques. The fact that there are so few particles showing mixed Fe state of charge suggests that it is nucleation of the new phase rather than the diffusion of Li inside the particles that is rate limiting for these conditions. (from Ref. 2)

 

Nanoporous Hydrogen Storage Materials:
We used quantitative energy dispersive spectroscopy (EDS) in the TEM to show that we can synthesize Pd-based materials with a thin layer of Rh at the surface. This Rh layer protects the nanoporous structure at elevated temperatures so that it is more stable and does not degrade the hydrogen storage properties.

References:
1. Cappillino, P.J., J.D. Sugar, M.A. Hekmaty, B.W. Jacobs, V. Stavila, P.G. Kotula, J.M. Chames, N.Y. Yang, and D.B. Robinson, Nanoporous Pd alloys with compositionally tunable hydrogen storage properties prepared by nanoparticle consolidation. Journal of Materials Chemistry, 2012. 22(28): p. 14013-14022.
2. Ong, M.D., B.W. Jacobs, J.D. Sugar, M.E. Grass, Z. Liu, G.M. Buffleben, W.M. Clift, M.E. Langham, P.J. Cappillino, and D.B. Robinson, Effect of Rhodium Distribution on Thermal Stability of Nanoporous Palladium-Rhodium Powders. Chemistry of Materials, 2012. 24(6): p. 996-1004.


A thin cross section of a nanopourous particle (left) shows that the nanoporous structure is still in tact near the particle surface where significant concentrations of Rh are present. Near the center of the particles, however, the porous structure has coarsened, and compositional analysis (right) shows that there is practically no Rh there. (from Ref. 2)


A thin, protective Rh layer is deposited on nanoparticles made using a dendrimer-encapsulation process. The scale bar is 5 nm. Because of the low Rh content and the small length scales here, it was necessary to use our aberration-corrected FEI Titan 80-200 with a large solid angle EDS detector (ChemiSTEM) for quantitative compositional analysis. In one synthesis route, we fabricate PdRh alloy particles (left side), and in another we fabricate particles with a core-shell structure (right side). (From Ref. 1)

Formation of Second-Phase Precipitates in Thermoelectric Compounds:
We studied the formation of second-phase precipitates in bulk thermoelectric compounds. We found that second phase precipitates can often form with a preferred crystallographic orientation relationship. The result is that the electron diffraction pattern can be misinterpreted as having superlattice reflections when it actually has multiple orientation variants of a second phase. We also showed that improvements in thermoelectric properties are best found when isolated precipitates are uniformly distributed in the bulk. This takes advantage of interface scattering and can exhibit enhanced transport properties. If the second phase precipitates form a percolating medium in the bulk, the transport properties approximate an average of the two phases.

1. Sugar, J. and D. Medlin, Solid-state precipitation of stable and metastable layered compounds in thermoelectric AgSbTe2. Journal of Materials Science, 2011. 46(6): p. 1668-1679.
2. Sharma, P.A., J.D. Sugar, and D.L. Medlin, Influence of nanostructuring and heterogeneous nucleation on the thermoelectric figure of merit in AgSbTe2. Journal of Applied Physics, 2010. 107(11): p. 113716-9.
3. Medlin, D.L. and J.D. Sugar, Interfacial Defect Structure at Sb2Te3 Precipitates in the Thermoelectric Compound AgSbTe2. Scripta Materialia, 2010. 62: p. 379-382.
4. Lensch-Falk, J.L., J.D. Sugar, M.A. Hekmaty, and D.L. Medlin, Morphological evolution of Ag2Te precipitates in thermoelectric PbTe. Journal of Alloys and Compounds, 2010. 504(1): p. 37-44.
5. Sugar, J.D. and D.L. Medlin, Precipitation of Ag2Te in the thermoelectric material AgSbTe2. Journal of Alloys and Compounds, 2009. 478(1-2): p. 75-82.


During precipitation of Sb2Te3 in super saturated AgSbTe2, planar defects (stacking faults in left images) can serve as a template for the nucleation of Sb2Te3 precipitates. The end result is a connected network of Sb2Te3 precipitates (right image) in which transport through the bulk does not require interfacial scattering (electrons and phonons stay in their respective phases). As a result, we do not observe an enhancement in thermoelectric properties. (From ref. 1 and 2)

Upon cooling cubic AgSbTe2 from the melt, monoclinic Ag2Te precipitates form. The electron diffraction pattern (top left) shows extra reflections that look like superlattice reflections. However, the simulated diffraction pattern (top right), and corresponding dark-field images (bottom) show that these extra reflections are actually 4 different preferred orientation variants of Ag2Te in cubic AgSbTe2. (From ref. 5) This type of precipitate morphology is useful for thermoelectric property enhancement (e.g. see Pei, Y.; Lensch-Falk, J.; Toberer, E. S.; Medlin, D. L.; Snyder, G. J. Advanced Functional Materials 2011, 21, (2), 241-249. & Faleev, S. V.; Léonard, F. Phys Rev B 2008, 77, 214304).

Volumetrically Confined Phase Separation:
Usually, at elevated temperature, metal films dewet ceramic substrates. In this study, we completely encapsulated metallic alloy wires in sapphire, which allowed us to suppress the normal modes of dewetting. As a result, we could resolidify the metal from a melt and reproducibly fabricate single crystal metal structures. An additional anneal for this CuNiFe alloy promoted phase separation and resulted in structures with a modulated composition alternating between Cu-rich and NiFe-rich phases.

1. Sugar, J.D., et al., Encapsulation-induced stabilization of dimensionally restricted metallic alloy wires. Acta Materialia, 2010. 58(16): p. 5332-5341.
2. Sugar, J.D., et al., Spatially confined alloy single crystals for model studies of volumetrically constrained phase transformations. Applied Physics Letters, 2006. 89(17).


In an unconstrained metal film, annealing at elevated temperature causes the film to dewet and results in isolated metal particles. Here, a homogenous CuNiFe alloy dewets and decomposes into a Cu-rich and NiFe-rich phase within each particle (shown in cross section). (from 1)


If the film is completely encapsulated in sapphire, dewetting is suppressed, and the metal particle retains its shape throughout the annealing process. The decomposition into two phases results in a modulated structure. (From 1).

 

Materials reasearch for lithium-ion batteries

In this clip, Sandia National Laboratories materials scientist Josh Sugar describes the technical approach taken by he and his colleagues when analyzing LiFePO4 (LFP) material for potential use in lithium-ion batteries.

 

Lithium-ion batteries

Sandia National Laboratories physicist Farid El Gabaly explains the need for a new kind of material in lithium-ion batteries, particularly for larger applications, and how lithium iron phosphate (LiFePO4, or LFP) might be the solution.

 

 

Publications


1. R. A. Marks, J. D. Sugar, D. T. Danielson and A. M. Glaeser, “Joining of Alumina via Microdesigned Cu/Nb/Cu Interlayers,” pp. 1127-1134 in Proceedings of the International Conference on Mass and Charge Transport in Inorganic Materials: Fundamentals to Devices, P. Vincenzini, V. Buscaglia (Editors), Techna Publishers S.R.L., Faenza, Italy, (2000).

2. R.A. Marks, J.D. Sugar, and A.M. Glaeser, "Ceramic joining IV. Effects of processing conditions on the properties of alumina joined via Cu/Nb/Cu interlayers." Journal of Materials Science, 2001. 36(23): p. 5609-5624.

3. R. A. Marks, J. D. Sugar, J. McKeown, M. R. Locatelli, K. Nakashima and A. M. Glaeser, “Transient Liquid Phase Joining of Ceramics: New Approaches to Materials Integration,” pp. 25-30 in Proceedings of the First International Symposium on Environmental Materials and Materials Recycling, (March 8-9, 2001, Osaka Japan) JWRI, Osaka (2001).

4. J.D. Sugar, J.T. McKeown, R.A. Marks, and A.M. Glaeser, "Liquid-film-assisted formation of alumina/niobium interfaces." Journal of the American Ceramic Society, 2002. 85(10): p. 2523-2530.

5. M. Kitayama, T. Narushima, K. Tran, J. Sugar, R. Gronsky and A. M. Glaeser, “Model Studies of Surfaces and Interfaces in Ceramic and Ceramic/Metal Systems,” pp. 38-46 in Proceedings of the 2nd Fulrath Memorial International Symposium on Advanced Ceramics, April 9th, 2003, Tokyo Japan.

6. J. D. Sugar, J. T. McKeown, T. Akashi, S. M. Hong, K. Nakashima, and A. M. Glaseser, “Transient-Liquid-Phase and Liquid-Film-Assisted Joining of Ceramics.” Journal of the European Ceramic Society, 2006. 26: p. 363-372.

7. J.T. McKeown, J.D. Sugar, R. Gronsky, and A.M. Glaeser, "Processing of Alumina-Niobium Interfaces via Liquid-Film Assisted Joining." Welding Journal, March 2005 p. 41s-50s.

8. J. T. McKeown, J. D. Sugar, S. Hong, T. Akashi and A. M. Glaeser, Transient-Liquid-Phase and Liquid-Film-Assisted Joining of Advanced Ceramics,” pp. 1-10, Proceedings of the 3rd Fulrath Memorial International Symposium on Advanced Ceramics, April 6th, 2005, Tokyo Japan.

9. J. T. McKeown, J. D. Sugar, R. Gronsky and A. M. Glaeser, “Effects of impurities on alumina-niobium interfacial microstructures,” Materials Characterization, 2006. 57(1): p.50-57.

10. S. M. Hong, T. Akashi, J. T. McKeown, J. D. Sugar, C. C. Bartlow and A. M. Glaeser, “Transient-Liquid-Phase and Liquid-Film-Assisted Joining of Ceramics,” Advances in Science and Technology, 2006. 45: p. 1568-1577.

11. J. D. Sugar, J. T. McKeown, A. M. Glaeser, and R. Gronsky, “Spatially confined alloy single crystals for model studies of volumetrically-constrained phase transformations,” Applied Physics Letters, 2006. 89: p. 173102-1-3.

12. J. D. Sugar & D. L. Medlin, “Precipitation of Ag2Te in the thermoelectric material AgSbTe2,” Journal of Alloys and Compounds, 2009. 478:p. 75-82.

13. D.L. Medlin and J. D. Sugar, “Interfacial Defect Structure at Sb2Te3 Precipitates in the Thermoelectric Compounds AgSbTe2,” Scripta Materialia 2010. 62:p. 379-382.

14. P.A Sharma, J. D. Sugar, and D. L. Medlin, “Influence of Nanostructuring and Heterogeneous Nucleation on the Thermoelectric Figure of Merit in AgSbTe2,” Journal of Applied Physics, 2010. 107(11): p. 113716-9.

15. J. Lensch-Falk, J.D. Sugar, M.A. Hekmaty, & D.L. Medlin, “Morphological Evolution of Ag2Te Precipitates in Thermoelectric PbTe,” Journal of Alloys and Compounds, 2010. 504(1): p. 37-44.

16. J. D. Sugar, J. T. McKeown, V. Radmilovic, A. M. Glaeser, and R. Gronsky, “Encapsulation-Induced Stabilization of Dimensionally-Restricted Metallic-Alloy Wires,” Acta Materialia, 2010. 58: p. 5332-41.

17. J. D. Sugar and D.L. Medlin, “Solid-state precipitation of stable and metastable layered compounds in thermoelectric AgSbTe2,” Journal of Materials Science, 2011. 46(6): p. 1668-1679.

18. Jeffries, J.R., Lima Sharma, A.L., Sharma, P.A., Spataru, C.D., McCall, S.K., Sugar, J.D., Weir, S.T., and Vohra, Y.K., “Distinct superconducting states in the pressure-induced metallic structures of the nominal semimetal Bi4Te3,” Physical Review B, 2011. 84(9): p. 092505.

19. Ong, M. D., Jacobs, B. W., Sugar, J. D., Grass, M. E., Liu, Z., Buffleben, G. M., Clift, W. M., Langham, M. E., Cappillino, P. J. and Robinson, D. B., “Effect of Rhodium Distribution on Thermal Stability of Nanoporous Palladium-Rhodium Powders,” Chemistry of Materials, 2012. 24(6): p.996-1004.

20. Cappillino, Patrick J., Sugar, Joshua D., Hekmaty, Michelle A., Jacobs, Benjamin W., Stavila, Vitalie, Kotula, Paul G., Chames, Jeffrey M., Yang, Nancy Y. and Robinson, David B., “Nanoporous Pd alloys with compositionally tunable hydrogen storage properties prepared by nanoparticle consolidation,” Journal of Materials Chemistry, 2012. 22(28): p.14013-14022.

21. Chueh, W. C., El Gabaly, F., Sugar, J. D., Bartelt, N. C., McDaniel, A. H., Fenton, K. R., Zavadil, K. R., Tyliszczak, T., Lai, W. and McCarty, K. F., “Intercalation Pathway in Many-Particle LiFePO4 Electrode Revealed by Nanoscale State-of-Charge Mapping,” Nano Letters, 2013. 13(3): p.866-72.

22. Sugar, Joshua D., El Gabaly, Farid, Chueh, William C., Fenton, Kyle R., Tyliszczak, Tolek, Kotula, Paul G. and Bartelt, Norman C., “High-resolution chemical analysis on cycled LiFePO4 battery electrodes using energy-filtered transmission electron microscopy,” Journal of Power Sources, 2013. 246: p.512-521.

 

Work Experience
2010 - present Staff Scientist, Sandia National Laboratories, Livermore, CA
2007 - 2010 Postdoctoral Appointee, Sandia National Laboratories, Livermore, CA

Education
2007 Ph.D., Materials Science and Engineering, University of California, Berkeley, CA
2003 M.S., Materials Science and Engineering, University of California, Berkeley, CA
2001 B.S., Materials Science and Engineering, University of California, Berkeley, CA