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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 phased array antennas and other phase shifting devices. The dielectric constant and the loss tangents have been reduced to enhance the overall impedance matching and thereby lowering the insertion loss of the device. In addition, the overall tunability, the change in the dielectric constant with applied voltage. is maintained at a sufficiently high level. The thickness limitation of the bulk materials is around 3-4 mils which can be used up to approximately 15 GHz. In order to increase the operating frequencies of the phase shifters. thick films were fabricated using non-aqueous tape-casting. The tapes were electrically characterized and compared to bulk ceramics. Also. laminated stacks of high dielectric constant and low dielectric constant alternating layers were fabricated.

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Polycrystalline (1−x)Ta2O5–xAl2O3 thin films were fabricated by metalorganic solution deposition technique on Pt-coated Si substrate at a temperature of 750 °C. Thin films with 0.9Ta2O5–0.1Al2O3 composition exhibited improved dielectric and insulating properties compared to Ta2O5 thin films. The measured small signal dielectric constant and dissipation factor at 100 kHz were 42.8 and 0.005, respectively. The temperature coefficient of capacitance was 20 ppm/°C in the measured temperature range of 25–125 °C. The leakage current density was lower than 6×10−8 A/cm2 up to an applied electric field of 1 MV/cm. A charge storage density of 18.9 fC/μm2 was obtained at an applied electric field of 0.5 MV/cm. The high dielectric constant, low dielectric loss, low leakage current density, and good temperature and bias stability suggest (1−x)Ta2O5–xAl2O3 thin films to be a suitable dielectric layer in integrated electronic devices in place of conventional dielectrics such as SiO2 or Si3N4.

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