Local Structure of the Proton Conducting System Ba2In1.85M0.15O5 (M = Ga, Sc, In, Y) Investigated with Infrared Spectroscopy

Abstract

This thesis concerns experimental studies on the proton conducting brownmillerite type oxide system, Ba2In1.85M0.15O5 (M = Ga, Sc, In, Y), of interest as potential proton conducting electrolytes for next-generation fuel cells operating in the temperature range from ~200 to ~500 °C. This temperature range is more suitable for practical applications but today’s available electrolytes do not show satisfactory performance. To develop new materials as electrolytes with better performances a deeper understanding of the structure and the proton dynamics of the material is required. Protons in the Ba2In1.85M0.15O5 (M= Ga, Sc, In, Y) system have been introduced by hydration. How the dopant atoms influence the structure and proton dynamics of the material is the key issue to understand. Using infrared spectroscopy, such properties have here been investigated. The results show that the material structure becomes distorted with incorporation of dopant atoms. Also the results show that the symmetry of material’s structure increases upon hydration. Furthermore, the results indicate that smaller atomic radius of the dopant results in a higher tendency of hydrogen bond formation between the protons and neighboring oxygens.