BARIUM STRONTIUM-TITANATE AND NONFERROELECTRIC OXIDE CERAMIC COMPOSITES FOR USE IN PHASED-ARRAY ANTENNAS

A ceramic ferroelectric phase shifting device has been demonstrated us ing Ba1-xSrxTiO3 (BSTO) ceramics.(1) As part of an effort to optimize the device performance, various composites of BSTO and other nonelectr ically active oxide ceramics have been formulated. In general the comp osites have reduced dielectric constants, epsilon', where epsilon = ep silon' - i epsilon'' and reduced loss tangents, tan delta, compared to BSTO. The low dielectric constant and low loss tangent reduce the ove rall impedance mismatch and insertion loss of the device. In addition, the tunability (change in the dielectric constant with applied voltag e) is maintained at a relatively high level (15% with an applied elect ric field of 1.5 V/mu m) for dielectric constants of 200. The combinat ion of electronic properties of these materials offer substantially hi gher operating frequencies, 10 GHz and above. The microstructures incl uding grain size and phase analysis have been examined using SEM and E DX. X-ray diffraction has been used to identify the presence of any se condary phases formed in the composites. The analysis of the phase for mation and compositional variations will be related to the electronic properties of the materials.