The papers included in this issue of ECS Transactions were originally presented in the symposium ¿Ionic and Mixed Conducting Ceramics 7¿, held during the 217th meeting of The Electrochemical Society, in Vancouver, Canada, from April 25 to 30, 2010.

The papers included in this issue of ECS Transactions were originally presented in the symposium ¿Ionic and Mixed Conducting Ceramics 6¿, held during the 213th meeting of The Electrochemical Society, in Phoenix, Arizona from May 18 to 23, 2008.

Advanced mixed ionic electronic conducting (MIEC) perovskites play an important role in many electrochemical systems for advanced energy technologies. They are major components in such devices as solid oxide fuel cells (SOFCs), oxygen separation membranes, chemical sensors and catalysts. In addition to energy technology, the development of these multifunctional materials is of crucial importance for transportation, aerospace engineering, and electronics. The use of these materials as chemical sensors is also important for anti-terrorism initiatives. The present book discusses progress and problems in the development of ionic, electronic, and MIEC materials as active materials in advanced energy systems; the development and design of solid-oxide fuel cells (SOFCs) for next-generation vehicles, chemical sensors and oxygen separation membranes; and identifies directions for future research, such as conducting mechanisms, stability and reliability of devices, degradation problems, crystal structure, classification of phase transitions exhibited by the materials.