Microstructures and dielectric tunable properties of Ba0.5Sr0.5TiO3–Li2MgTiO4 and Ba0.5Sr0.5TiO3–Li2Mg3TiO6 composite ceramics

(1− x )Ba 0.5 Sr 0.5 TiO 3 – x Li 2 MgTiO 4 and (1− x )Ba 0.5 Sr 0.5 TiO 3 – x Li 2 Mg 3 TiO 6 composite ceramics were prepared via the conventional solid-state reaction method. Microstructures and dielectric tunable properties of Ba 0.5 Sr 0.5 TiO 3 –Li 2 MgTiO 4 and Ba 0.5 Sr 0.5 TiO 3 –Li 2 Mg 3 TiO 6 composite ceramics were investigated. In this composite system, the cubic perovskite BST phase can coexist well with the rock-salt Li 2 MgTiO 4 phase and Li 2 Mg 3 TiO 6 phase. Only at 1300 °C sintering temperature, due to the decomposition of Li 2 MgTiO 4 , a trace of Mg 2 TiO 4 impurity is produced when dielectric content is higher than 55wt% in Ba 0.5 Sr 0.5 TiO 3 –Li 2 MgTiO 4 composite ceramics. At the test frequency of 10 kHz, with the increase of Li 2 MgTiO 4 content from 10wt% to 60wt%, the dielectric constant of Ba 0.5 Sr 0.5 TiO 3 –Li 2 MgTiO 4 composite ceramics sintered at 1300 °C decreases from 962 to 90, the dielectric loss remains below 0.009, and the tunability under an electric field strength of 3 kV/mm gradually decreases from 12.1 to 4.2%. With the gradual increase of Li 2 Mg 3 TiO 6 content from 10 wt% to 60 wt%, the dielectric constant of Ba 0.5 Sr 0.5 TiO 3 –Li 2 Mg 3 TiO 6 composite ceramics sintered at 1280 °C decreases from 1042 to 79, the dielectric loss remains below 0.003, and the tunability at 3 kV/mm decreases from 17.2 to 4.9%.