Preparation and Characterization of Electrolyte Materials for Proton Conducting Fuel Cells.

摘要

Experiments were conducted to test and characterize proton conducting electrolyte materials and layers formed by solid state reactions. Screen printed layers of yttrium doped ceria and alkaline earth carbonates were reacted at high temperatures on NiO-YSZ and NiO-CGO substrates with the intent of forming thin and dense A2+B4+O 3 based perovskite layers. The layers were investigated and characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy and x-ray diffraction analysis. The influence of dopant (M = Nd, Eu, Gd, Y, Yb) and atmosphere on the protonic conductivity of sintered BaCe0.5Zr 0.4M0.1O2.95 pellets was investigated through impedance spectroscopy.;The layer synthesis method showed promise for producing thin and dense layers of barium and strontium cerates as well as barium, strontium and calcium zirconates. The perovskite tolerance factor, a measure of the deviation from the cubic lattice, seems to correlate to the selective reactivity in the layer synthesis. Proton conduction was found to be predominant in hydrogen containing atmospheres in the low to intermediate temperature range (300-600°C) with increased competition from alternative charge carriers as temperature increased. The highest protonic conduction was found in Yb doped BaCe0.5Zr 0.4M0.1O2.95 samples. Dopants with smaller ionic radii resulted in improved tolerance factors, decreased likelihood of A-site doping and higher conductivities.