ELECTROLYTE FILMS BASED ON HIGH TEMPERATURE PROTON CONDUCTORS FOR IT-SOFCs APPLICATION

Abstract

High temperature proton conductors (HTPCs) have a wide range of applications and the most important are electrolytes for solid oxide fuel cells (SOFCs) and membranes for hydrogen separation. Among these materials doped barium cerates BaCe1-xYxO3-´ (BCY) have show the highest proton conductivities, but these materials are not stable in CO2 at intermediate temperatures. This instability of doped barium cerates limits their application for commercial SOFCs, because in this case hydrocarbon fuels can not be used for fuelling. Although there were many attempts to stabilize doped barium cerates in CO2, the problem of instability in CO2 is still not solved. Another problem correlated with HTPCs is poor sinterability which, as a consequence, has high internal resistivity of electrolyte i.e. high grain-boundary resistance.The main aim of this research is to synthesize films of barium cerate based electrolytes for SOFC with good stability in CO2 atmosphere and with lower bulk and grain boundary resistivity compared with the literature data. To achieve this objective the several approaches will be used such as to process BCY based electrolyte in form of thin or thick films using tape casting as well as radio-frequent (RF) sputtering of synthesized fine powders. Several dopants such as Co, Zr, Nb, Ta and In will be used in different concentrations to improve the stability of the BCY based electrolyte. To decrease the resistivity of the electrolyte, attempts will be made to increase grain size as well to grow the films with columnar grains.All electrolyte powders will be synthesized using citric-nitric auto-combustion (CNA) method. Cermet anode substrates will be produced using method of evaporation and decomposition solutions and suspensions (EDSS). Application of the above mentioned methods will enable preparation of nanopowders with high sinterability. Stable electrolyte powders will be used for fabrication of functional intermediate temperature solid oxide fuel cells (IT-SOFCs).