Adventures in Phase Diagrams: Crystal-Chemical Sagas of Complex Titanates for Talking Ceramics. T.A. Vanderah, Ceramics Division, National Institute of Standards and Technology, Gaithersburg, MD 20899

Dielectric ceramics used as essential components in microwave communication systems must possess high permittivity, high Q factor (i.e. low dielectric loss), and zero or low temperature coefficient and frequency dependence of the permittivity. This coincidence of properties is found in complex titanium oxide systems (among a very few others). Recent experimental phase diagram determinations have included the BaO-Fe₂O₃-TiO₂, SrO-TiO₂-Nb₂O₅, and BaO-TiO₂-Ta₂O₅ ternary systems. Highlights and trends in the crystal chemistry found in these systems will be discussed, including some unusual structural behavior that may or may not be related to unusual dielectric properties indicated by preliminary capacitive measurements. Chemistry-structure-property relationships in this class of electronic oxides remain essentially uncharted.