Microwave dielectric properties and low sintering temperature of Ba0.5Sr0.5TiO3–Mg2TiO4 composites synthesized in situ by the hydrothermal method

(1−x)Ba0.5Sr0.5TiO3–xMg2TiO4 composite ceramics were synthesized in situ by the hydrothermal method and their structure and dielectric properties were investigated systematically. Results showed that a ferroelectric–dielectric composite containing Ba0.5Sr0.5TiO3 and Mg2TiO4 phases could be successfully synthesized at sintering temperatures below 1300 °C. As the sintering temperature increased, the dielectric peaks of the cubic-tetragonal phase transition were markedly enhanced and sharpened and shifted toward high temperature. As the concentration of Mg2TiO4 increased, both permittivity (ε) and tunability (T) decreased, whereas Q value firstly increased and then decreased. The sample with x=0.6 exhibited good microwave dielectric properties, with ε of 136, Q of 342 (at 3.804 GHz) and T of 16.2%, which make it a potential candidate for the fabrication of tunable microwave devices.