Micro solid oxide fuel cells on glass ceramic substrates

Miniaturized solid oxide fuel cells are fabricated on a photostructurable glass ceramic substrate (Foturan) by thin film and micromachining techniques. The anode is a sputtered platinum film and the cathode is made of a spray pyrolysis (SP)-deposited lanthanum strontium cobalt iron oxide (LSCF), a sputtered platinum film and platinum paste. A single-layer of yttria-stabilized zirconia (YSZ) made by pulsed laser deposition (PLD) and a bilayer of PLD-YSZ and SP-YSZ are used as electrolytes. The total thickness of all layers is less than 1 μm and the cell is a free-standing membrane with a diameter up to 200 μm. The electrolyte resistance and the sum of polarization resistances of the anode and cathode are measured between 400 and 600 °C by impedance spectroscopy and direct current (DC) techniques. The contribution of the electrolyte resistance to the total cell resistance is negligible for all cells. The area-specific polarization resistance of the electrodes decreases for different cathode materials in the order of Pt paste > sputtered Pt > LSCF. The open circuit voltages (OCVs) of the single-layer electrolyte cells ranges from 0.91 to 0.56 V at 550 °C. No electronic leakage in the PLD-YSZ electrolyte is found by in-plane and cross-plane electrical conductivity measurements and the low OCV is attributed to gas leakage through pinholes in the columnar microstructure of the electrolyte. By using a bilayer electrolyte of PLD-YSZ and SP-YSZ, an OCV of 1.06 V is obtained and the maximum power density reaches 152mW cm^-2 at 550°C.