Synthesis, characterization and electrical porperties of oxide–ion conductors

Abstract

Oxide ion conductors have been attracted much attention during past years in view of its potential applications in many solid oxide devices; especially in solid oxide fuel cells (SOFCs).Many oxide ion conductors of BIMEVOX family have been demonstrated to be good candidates for SOFC application due to their high ionic conduction at moderate temperatures. It has been found that almost all studies BIMEVOX materials are conventionally prepared by solid state reactions. Although, the solid state reaction is widespread used for preparation of oxide ion conductors, it offers several disadvantages. This research work titled «Synthesis, characterization and electrical properties of oxide ion conductors» has been devoted to synthesize new oxide ion conductors of the BIMEVOX family, employing two alternative methods of preparation, namely sol gel and microwave assisted synthesis, which are more recently originated for preparing homogeneous single phase solids with the ensuring time and energy savings. The present Ph.D. thesis is divided into five main chapters, which can be summarized as follows: CHAPTER ONE: General Introduction newlineFuel cells are electrochemical energy devices in which the electricity is generated at the electrode/electrolyte interface through chemical reactions. The electrolyte is the most important and indispensable part of the fuel cell, which permits ion transport between the electrodes. The fuel cells are categorized based on mobile ionic species that electrolyte can conduct: (i) Proton exchange membrane fuel cells (PEMFC). (ii) Alkaline fuel cells (AFC). (iii) Phosphoric acid fuel cells (PAFC). (iv) Molten carbonate fuel cells (MCFC). (v) Solid oxide fuel cells (SOFC). The main advantage of SOFC over other fuel cells is that it has the highest electrical efficiency (60 %) at high operation temperatures ( gt 700 oC). SOFCs are based on an oxide ion conductor, which allows the migration of oxide ions, O2 from the cathode to the anode and thereafter react with the fuel to generate electrical power.