*** 970635 Donahue This Small Business Innovation Research Phase I project will be directed toward the fabrication and performance evaluation of a new generation of oxygen anion conducting solid electrolytes. The new materials based on oxygen deficient brownmillerite lattices are expected to have a near term potential for achieving high ionic conductivities at relatively lower temperatures. There are strong incentives to develop solid electrolytes for application in electrochemical cells and sensors. The performance of these devices would be significantly enhanced by realizing higher ionic conductivity at lower temperatures than is currently realized in the yttria stabilized zirconia. It would, for example, enable fuel cell technology to be economically competitive by reducing the severe materials constraints on hardware due to the high operating temperatures of the current system. Moderate temperature electrochemical devices based on such advanced solid electrolytes will only require relatively inexpensive stainless steel hardware components for their implementation. Successful completion of this program will result in identifying a new generation of oxygen anion conducting solid electrolytes for application in intermediate temperature electrochemical devices. ***