Medium-temperature solid oxide fuel cells prepared using reactive magnetron sputtering. Ph.D. Thesis

Thesis/Dissertation · Fri Dec 31 04:00:00 EST 1993

OSTI ID:135414

Wang, L

The purpose of this research is to investigate the deposition, structure, interfacial impedances, and characteristics of medium temperature solid-oxide fuel cells (SOFC`s) with thin-film electrolytes. Three main areas have been investigated. First, the structure, chemistry, and properties of materials designed specifically for medium temperature SOFC`s have been studied. The authors have developed techniques for sputter deposition of cubic 10 mol percent Y2O3-stabilized zirconia (YSZ) and 30 mol percent Y2O3-doped bismuth oxide (YSB) thin film oxygen ion conductors. The electrical properties of the films were characterized using the complex impedance spectroscopy method. Studies of AgYSZ cermet and Ag-perovskite (perovskite = La(1-x)Sr(x)Co(Mn)O3), used as high conductivity, low overpotential air electrodes, have also been carried out. Second, interfacial impedances for various electrode-electrolyte combinations and for multilayer electrolytes have been studied. In particular, the authors have found that a layer of Y-stabilized Bi2O3 (YSB) as thin as 60 nm between the YSZ electrolyte and the electrode significantly reduces the interfacial resistance. For example, inserting YSB between YSZ and a Ag-YSZ electrode reduces the resistance from 1.5 to 0.45 Omega cm(exp 2) at 750 deg C in air. Ag-(La,Sr)CoO3 on YSB electrolytes had interfacial resistances as low as 0.3 Omega cm2, compared with 0.4 and 1.5 Omega cm(exp 2) for (La,Sr)CoO3 and Ag on YSB at 750 deg C, respectively. The Ag cermet materials thus exhibited lower interfacial resistances than their component materials. Third, thin film medium temperature SOFC`s have been fabricated and characterized. SOFC`s were deposited onto porous alumina supports. The resulting cell open-circuit voltages (OCV) were approximately equal to 0.8 V, 0.3 V less than expected, due to gas cross-over.

• Research Organization: Northwestern Univ., Evanston, IL (United States)
• OSTI ID: 135414
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
DEPOSITION
ELECTRIC CONDUCTIVITY
ELECTRIC IMPEDANCE
ELECTROLYTES
INTERFACES
PERFORMANCE
SOLID ELECTROLYTE FUEL CELLS
THIN FILMS