Prof. Sossina Haile

Assistant Professor of Materials Science

Sossina Haile received her B.S and Ph.D from the Massachusetts Institute of Technology , and M.S, from the University of California, Berkeley. She has received the NSF National Young Investigator Award (1994-99), Humboldt Fellowship (1992-93), Fulbright Fellowship (1991-92), AT&T Cooperative Research Fellowship (1986-92). She is the recipient of the 1997 TMS Robert Lansing Hardy Award.

Sossina Haile's research centers on ionic conduction in solids, with the twin objectives of understanding the mechanisms that govern ion transport, and applying such an understanding to the development of advanced solid electrolytes and novel solid-state electrochemical devices. Technological applications of fast ion conductors include batteries, sensors, ion pumps and fuel cells. It is in this last area that Dr. Haile's work is expected to have the most impact.

Materials under investigation in Dr. Haile's group include proton-conducting perovskites, mixed oxygen- and electron-conducting perovskites, oxygen-conducting oxides, and proton-conducting solid acid compounds. Because ionic conductivity is closely tied to the crystal structure of and structural transitions in the conducting solid, crystal growth, structure determination by X-ray and neutron diffraction, and thermal analysis are important aspects of Dr. Haile's research. Using these techniques, her group has shown, for example, that the ordering transition in gadolinium zirconate from the fluorite to the pyrochlore structures is second order in nature and is accompanied by an increase in oxygen ion conductivity. In another example, her group has demonstrated that grain boundary transport in Gd-doped BaCeO3, a potential electrolyte for solid oxide fuel cells, cannot explain the high conductivity of this material, in contrast to speculations in the literature. Dr. Haile's work is supported by the National Science Foundation, via a National Young Investigator Award, and the Electric Power Research Institute.

Selected Publications

Proton Conducting Perovskites

• S. M. Haile and D. L. West "Kinetics of Isotope (H/D) Exchange in Gadolinia-Doped Barium Cerate," submitted, J Appl. Phys.

• S. M. Haile, D. L. West and J. Campbell "The Role of Microstructure and Processing on the Proton Conducting Properties of Gadolinium-Doped Barium Cerate," in the press, J. Mat. Res.

• D. Shima and S. M. Haile "The Influence of Cation Non-Stoichiometry on the Properties of Undoped and Gadolinia-Doped Barium Cerate," Solid State Ionics, 97 (1997) 443-447.

• D. West, S.M. Haile and R. Feigelson, "Synthesis and Characterization of Single Crystal and Polycrystalline Gd-Doped Barium Cerate," Mat. Res. Soc. Symp. Proc., 393 (1995) 31-36.

Solid Acid Compounds

• S.M. Haile, P. Calkins and D. Boysen, "The structure and vibrational spectrum of b-Cs₃(HSO₄)₂(H_2-x(P_1-x,S_x)O₄)
  (x ~ 0.5), a new superprotonic conductor, and a comparison with a-Cs₃(HSO₄)₂(H₂PO₄)," submitted, J. Sol. State Chem.

• S.M. Haile and P. Calkins, "X-ray diffraction study of Cs₅(HSO₄)₃(H₂PO₄)₂, a New Solid Acid with a Unique Hydrogen-Bond Network," submitted, J. Sol. State Chem.

• S.M. Haile, P. Calkins and D. Boysen, "Superprotonic Conductivity in
  b-Cs₃(HSO₄)₂(H_x(P,S)O₄)," Solid State Ionics, 97 (1997) 145-151.

• S.M. Haile, K.-D. Kreuer and J. Maier, "The Structure of Cs₃H₄(SO₄)₂(PO₄) -- a New Compound with a Superprotonic Transition," Acta Cryst B51 (1995) 680-687.

• S.M. Haile, G. Lentz, K.-D. Kreuer and J. Maier, "Superprotonic Conductivity in Cs₃H₄(SO₄)₂(PO₄)," Solid State Ionics 77 (1995) 128-134.

Alkali Ion Conducting Silicates

• S.M. Haile and B.J. Wuensch, "Comparison of the crystal-chemistry of selected (MSi₆O₁₅)-based silicates," Amer. Min., 82, (1997) 1141-1149.

• S.M. Haile, B.J. Wuensch, R.A. Laudise and J. Maier, "The Structure of Na₃NdSi₆O₁₅•2H₂O-- A Layered Silicate with Paths for Possible Fast Ion Conductor," Acta Cryst. B53 (1997) 7-17.

• S.M. Haile, B.J. Wuensch, R.A. Laudise and J. Maier, "The Structure of Na₃YSi₆O₁₅ -- A Unique Silicate Based on Discrete Si₆O₁₅ Units and a Possible Fast Ion Conductor," Acta Cryst B51 (1995) 673-680.

• S.M. Haile, B.J. Wuensch and R.A. Laudise, "Hydrothermal Synthesis of New Alkali Silicates I. Potassium Neodymium Phases & II. Sodium Neodymium and Sodium Yttrium Phases," J. Cryst. Growth 131 (1993) 352-372 & 373-386.

• S.M. Haile, B.J. Wuensch, T. Siegrist and R.A. Laudise, "Conductivity and Crystallography of New Alkali-Rare Earth Silicates Synthesized as Possible Fast Ion Conductors," Solid State Ionics 53-56 (1992) 1292-1301.