Electric-Field-Controlled Permittivity Ferroelectric Composition for Microwave LTCC Modules

A low-temperature cofired ferroelectric ceramic composition for electrically tunable radio frequency devices is introduced. A sintering temperature of 950°C for BaSrTiO3–MgO was obtained following the combined addition of B2O3 and Li2CO3. The effects of these sintering aids on densification, microstructure, and ferroelectric properties were investigated. The permittivity and dissipation factor values were 234 and 0.0010, respectively, measured at 286.3 K, 1 kHz. The electrically tunable ferroelectric structure for microwave measurement was fabricated throughout the tape-casting process. Measured permittivity was 130 at 26 GHz and tunability >15% (4 V/μm).