Fabrication and characterization of barium strontium titanate and non-ferroelectric oxide composites for use in phased array antennas and other electronic devices

Abstract

A ceramic ferroelectric phase shifting device has been demonstrated using Ba/sub 1-x/Sr/sub x/TiO/sub 3/ (BSTO) ceramics. As a part of an effort to optimize the electronic device performance in the phase shifter, various composites of BSTO combined with other nonelectrically active oxide ceramics have been formulated. In general, the composites have reduced dielectric constants, /spl epsi/', where /spl epsi/=/spl epsi/'-i/spl epsi/, and loss tangents, tan /spl delta/. The low dielectric constant and low loss tangent reduce the overall impedance mismatch and the insertion loss of the device. In addition, the overall tunability, change in the dielectric constant with applied voltage, is maintained at a relatively high level. The combination of electronic properties of these materials offer substantially higher operating frequencies, 10 GHz and above. Another application for one of the composites is for use as a capacitor-varistor surge protector. The microstructures including grain size and phase analysis have been examined using SEM and X-ray diffraction. The analysis of the phase formation, compositional variations, and grain size will be related to the electronic properties of the materials.