STRUCTURAL INVESTIGATIONS OF MICROWAVE TITANATE CERAMICS. W. Wong-Ng, A. R. Drews, T. A. Vanderah, R. S. Roth, L. A. Bendersky, Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899

Dielectric ceramics are used extensively in the wireless communications industry. Very high dielectric constant ([[kappa]]) materials with low dielectric loss are of interest because of the possibility of miniaturization of electrical components. However, some high-[[kappa]] materials have large temperature coefficients (T_[[kappa]]) of the dielectric constant under typical operating conditions (e.g. SrTiO₃). Therefore, phases with improved properties, or phases that exist in equilibrium with SrTiO₃ which have T_[[kappa]]-values with the opposite sign could be useful in producing multiphase materials with a zero overall T_[[kappa]] and have promising properties for the development of advanced microwave resonators.

We have examined numerous compositions in preparing the phase diagrams for the BaO-Fe₂O_3-TiO₂ and SrO-Ti₂O₃-Nb₂O₅ systems. These diagrams provide processing-map information for modifying the properties of important ceramics. In the course of this investigation, we encountered a number of new compounds. A total of 16 ternary compounds were found in the BaO-Fe₂O₃-TiO₂ system and at least 4 in the SrO-Ti₂O₃-Nb₂O₅ system. In this report, we describe the results of structural studies of various compounds found in these systems.