Low loss microwave ferroelectric ceramics for high power tunable devices

In this paper we report the influence of the composition and concentration of Mg-containing additions such as Mg2TiO4, MgO and a mixture of Mg2TiO4–MgO on ceramics based on a mixture of BaTiO3/SrTiO3. Phase relations, crystal structure, microstructures, microwave dielectric properties (ɛ, tan δ) and DC tunability have been studied over a wide range of frequencies. The temperature dependence of the dielectric properties has been measured as well. Among the compositions synthesized were low loss bulk ferroelectrics with dielectric constants in the range 150–800 and relatively high DC tunabilities (up to 1.49 under a DC electric field of 40 kV/cm). These materials can be used for high power tunable microwave devices.