Study of transition metals doped strontium zirconate manganite for solid oxide fuel cell applications

Abstract

Environment-friendly, better efficiency, and fuel flexibility have made solid oxide fuel cells (SOFCs) a popular alternative to conventional combustion energy generating systems. However, despite having many advantages, the wide-scale commercialisation of SOFCs is still hampered by its cost and incompatibility of the different components. High operating temperature (and#8805;1000and#8451;) leads to a higher start-up time with increased electrode kinetics. Therefore, research nowadays is focused on the development of materials for intermediate-temperature (600-800and#8451;) and low-temperature (lt600and#8451;) range SOFCs. Among all the components of SOFC, the cathode is a vital component. It should have mixed conductivity, i.e. electronic and ionic conductivity. Mixed conducting materials have a pronounced effect on the oxygen reduction reaction since their presence increases the triple-phase boundary, thus, lowering the operating temperature, forming the core of this thesis. Mainly, perovskite-based materials have been studied for use as SOFC cathode materials for a long time due to their ability to accommodate a range of elements from the periodic table, inherent vacant sites and ability to accommodate multiple cations as dopants. Therefore, in this thesis, the effects of transition metal (Cu2+ and Ni2+) doping on the structural, thermal and conducting properties of strontium based perovskite (ABO3) materials (SrZrO3 and SrMnO3) are studied. The doping has been done at the B-site of the ABO3 type materials to enhance their conducting properties, match coefficient of thermal expansion (CTE), and increase the sinterability of Sr-based perovskites. Selected samples exhibiting comparable structural and thermal properties with a boro-silicate glass sealant and a standard interconnect material are also analysed for structural and thermal compatibility of developed materials. The thesis is divided into seven chapters with an overview in the beginning and a list of cited references at the end of each chapter.