Synthesis, Structure and Proton Conduction of Substituted BaTiO3 and BaZrO3 Perovskites

Doctoral thesis, 2013

Proton conducting oxides can be beneficial as electrolyte materials in devices such as fuel cells, hydrogen sensors etc. Proton conducting fuel cells (PCFCs), utilising H2 as fuel, stand out as a promising technology for future clean energy generation. The works herein is devoted to improve the performance of current state of the art perovskite structured BaZrO3 based electrolyte materials as well as synthesise and characterise novel electrolytes within the BaTiO3 based systems. Usually acceptor doping of these perovskites allows for proton conductivity in hydrogen containing atmosphere. In this thesis heavily co-doped strategy along with the impact of addition of sintering aid (ZnO) and various synthesis routes in BaZrO3 based materials is being tested. Heavily doped BaTiO3 based systems are also synthesised for the first time and characterised with an emphasis on proton conduction. This work is based on techniques such as X-ray powder diffraction studies, neutron powder diffraction, thermogravimetric analysis and AC impedance spectroscopy. In addition a neutron total scattering study is employed for the first time to understand the local structural environment for the deuteron position in a proton conducting electrolyte. Co-doping and sintering aid (in solution synthesis) for the In/Yb:BaZrO3 electrolyte seems to be beneficial. Heavily substituted Sc/In:BaTiO3 materials also show enhanced proton conductivity.