Fabrication and Characterization of Barium Strontium Titanate and Non-Ferroelectric Oxide Composites

Abstract

Various composites of BSTO combined with other nonelectrically active oxide ceramics have been formulated. In general, the composites have adjustable electronic properties which can be tailored for use in various electronic devices. Two applications, which are of interest in regard to the composites being discussed here, are phased array antennas and capacitor-varistor monolithic devices. For the phased array antennas, these properties include reduced dielectric constants, ε′, where ε = ε′ - iε″, and loss tangents, tan δ. The reduction of the dielectric constant and lowering of the loss tangents reditce 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 sufficiently high level for all dielectric constants of interest. Another application (for one of the composite materials) is a combined capacitorvaristor device. In general, this would be used to protect against spurious voltage surges and voltage transients in electronic micro-circuits. The microstructures, including grain size and phase analysis, have been examined using SEM and X-ray diffraction.

Voltage-controlled ferroelectric lens phased arrays

“…The materials are bulk oxide-ceramic composites of barium strontium titanate oxide (BSTO). ARL has also developed a simple, low-cost processing technique for their manufacturing [6]- [8]. It involves mixing barium titanate (BaTiO ) and strontium titanate (SrTiO ) powders.…”

Two low-cost phased arrays

“…Our recent inquiry into those losses [6,7] indicated that the possibility of developing ferroelectric materials with losses low enough to be useful for traveling wave antenna is remote. For these reasons, our efforts are being concentrated in developing a ferroelectric lens, which is discussed in the next section.…”