Structural disorder and transport in ternary oxides with the pyrochlore structure. Final report; FINAL

This research program has focused on the structure-electrical property relations in families of pyrochlore compounds which exhibit, on the one hand, controlled levels of structural disorder and on the other, controlled levels of ionic and electronic conductivities. Models have been developed to evaluate the often complex defect chemistry of these systems. Much progress has been made in extracting key thermodynamic and kinetic data. From a technological standpoint, novel solid electrolytes and compatible mixed conducting electrodes have been identified and the concept of the single phase monolithic fuel cell design has been demonstrated and patented. Related work on lanthanum gallate-based perovskites has shown even more promising results for use of such materials in the monolithic fuel cell structures. Recent work on the Bi(sub 3)Zn(sub 2)Sb(sub 3)O(sub 14) Pyrochlore, a phase found at grain boundaries in varistors, was also completed. This material was found to be a mixed ionic-electronic conductor with interesting implications for grain boundary equilibration kinetics in SnO-base varistor materials. Three of the most recent projects are summarized in this paper. The results of work on the perovskites are reported in recent publications