The microwave ceramic Ba(Y,Sb)0.05Ti0.90O3, based upon random B-site dipole-like substitutions is structurally and electrically characterized over the temperature range −55°C to 120°C. X-ray diffraction information coupled together with scanning electron microscopy reveals that the material is single phase and has submicron grain sizes. Results show the tetragonal phase ranges from −30°C to 200°C, which is a broader temperature range than that of the parent material BaTiO3, 0°C to 120°C. The material Ba(Y,Sb)0.05Ti0.90O3 also has a diffuse relative high dielectric constant of about 10,000 that peaks at the orthorhombic-tetragonal structural phase transition around −30°C.

Ferroelectrics are presently of interest for phase shifters, filters, and true time delay devices. Voltage tunable paraelectrics have the potential to lower device cost and reduce power consumption compared with presently available devices. In order to improve device performance to acceptable levels, materials must have high tunability, low dielectric constant, low loss tangent, and low leakage current. Using existing predictive techniques, compositions of Ba 0.6 Sr 0.4 TiO 3 -based ferroelectrics with charge-compensated substitutions for Ti 4+ were synthesized. Results of capacitance measurements are used to obtain dielectric constant and tunability in the paraelectric ( T > T C ) regime. The relevance to device requirements is discussed. Results for substituted samples are compared to those for (unsubstituted) Ba 0.6 Sr 0.4 TiO 3 . Discussion of the impact of the results on predictive techniques for tunability is addressed.

Substitution on B-sites in the perovskite oxide system Ba1-xSr1-xTiO3, has yielded materials suitable for relatively ternperature-insensitive, electric-field-tunable microwave devices. Single-phase cubic perovskites whose properties include room-temperature tunabilities as large as 30% at 1 V/mum and nearly temperature-independent dielectric constant and tunability over most of the military specified temperature range, -55 to 125 degreesC, have been achieved for 10 Hz less than or equal to f less than or equal to 1 MHz in the charge compensated system Ba1-xSrxTi1-2yCyDyO3, where C is Ho, Er, Tm, Lu, Sc, Y. or In. and D is Ta or Sb, with 0 less than or equal to x less than or equal to 0.2, and 0 < y less than or equal to 0.10.

Thin films were prepared from bulk targets by pulsed-laser deposition techniques. The targets were composed of Ba0.6Sr0.4TiO3 with charge-compensated substitutions for Ti4+. Results of the dielectric characterization measurements will be discussed and compared to the results of similar measurements in bulk materials with the same composition.

Ba0.6Sr0.4(YTa)yTi1-2yO3 has been shown to have properties which are promising for tunable applications requiring low dielectric constant [1]. Ba0.6Sr0.4(YTa)yTi1-2yO3 withy = 0.10 has been synthesized and well-characterized using x-ray diffraction, EDAX, and Raman Spectroscopy. The dependence of the dielectric properties on concentration, y, of Y and Ta are discussed along with implications for improved performance in device applications.