New Ordered Perovskite Dielectrics For Microwave Applications

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With their ability to sustain an outstanding dielectric response in the microwave region and accommodate extensive chemical substitution, oxide perovskites (ABO3) are the most widely studied and technologicallyimportant family of microwave dielectrics. For mixed-metal perovskites, where the A or B (or both) positions in the structure contain mixtures of different cations, a correlation between a high quality factor (low dielectric loss) and improved cation order has been clearly established. However, only a limited sub-set of ordered perovskite-forming stoichiometries has been examined, and many new systems are still to be explored. This proposal uses new approaches based on "non-integer" valence A-site chemistries to stabilize several completely new families of B-site ordered perovskites suitable for application as low-loss dielectrics in microwave communications. Many of the new materials lie in systems known to exhibit low melting points and high reactivity at low temperature, which also make them potentially useful for applications in low temperature co-fired ceramic (LTCC) technology.The unique electrical properties of ceramic microwave dielectric oxides have revolutionized microwave-based communications by reducing the size and cost of resonators, filters, and oscillators in systems ranging from cellular telephones to global positioning technologies. Although the existing materials are adequate for current applications the next generation of systems requires new materials with an enhanced dielectric response. The research in this proposal is aimed toward identifying these materials by using a novel design strategy to prepare new families of ceramic microwave dielectrics based on the perovskite structure.