Sossina M. Haile - Career

Career

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 to this last area that Dr. Haile's work is most closely tied.

Materials under investigation in Dr. Haile's group include proton-conducting solid acid compounds, proton-conducting perovskites, mixed oxygen- and electron-conducting perovskites, oxygen-conducting oxides, and alkali-conducting silicates. The standard technique used in her group for the characterization of electrical properties is A.C. impedance spectroscopy. 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 also important aspects of Dr. Haile's research. Using these methods, her group has shown, for example, that a broad range of proton containing solids undergo a monoclinic to cubic transition that is accompanied by an increase in conductivity of several orders of magnitude. In another example, her group has demonstrated that Ba0.5Sr0.5Co0.8Fe0.2O3-d has exceptional activity as a cathode for ceria-based solid oxide fuel cells. Dr. Haile's work in solid state ionics is supported by the National Science Foundation (NSF), the Army Research Office and the Department of Energy. In the past, support has also been provided by the Defense Advanced Research Projects Agency (DARPA), the Office of Naval Research, the California Energy Commission, the Powell Foundation and the Kirsch Foundation. Industrial support has been provided by General Motors, EPRI (formerly Electric Power Research Institute), HRL (formerly Hughes Research Labs) and Honeywell (formerly Allied Signal and now General Electric).

Beyond the field of solid state ionics, Haile's research also encompasses the investigation of structure-property relations in thermoelectric materials, in collaboration with colleagues at the Jet Propulsion Laboratory, and ferroelectric materials as part of a multidisciplinary program at Caltech dedicated to the computational prediction/optimization of material and device behavior. The former project is supported by NSF through the Caltech Center for the Science and Engineering of Materials. The latter is supported by the Army Research Office.

While new materials discovery and understanding are central themes in many of Haile's programs, device development plays an increasingly important role in her research. Micropower generators, based on solid oxide fuel cells are particularly attractive for portable power and are the subject of a recently concluded DARPA project in her group. Similarly, microactuators and micropumps based on ferroelectric thin films hold promise for advancing Microelectromechanical systems technology and development efforts are sponsored by an ARO MURI program. The transition from novel materials to useful devices requires the collective efforts of researchers from a broad range of fields, and both programs are highly interdisciplinary in nature.