Microstructures and dielectric tunable properties of Ba0.5Sr0.5TiO3–MgO–Mg2TiO4 composite ceramics

Ba0.5Sr0.5TiO3–MgO–Mg2TiO4 composite ceramics were prepared by a solid-state reaction method, and the dielectric tunable properties were investigated. It is observed that the addition of MgO–Mg2TiO4 into the Ba0.5Sr0.5TiO3 forms ferroelectric (Ba0.5Sr0.5TiO3)–dielectric (Mg2TiO4–MgO) composites. Increasing Mg2TiO4 content causes an increase of Curie temperature Tc towards room temperature and a decrease of dielectric constant peak εmax. The dielectric constant and loss tangent of Ba0.5Sr0.5TiO3–MgO–Mg2TiO4 composites have been reduced and the overall tunability is maintained at a sufficiently high level. With the increase of Mg2TiO4 content and the decrease of MgO content, the dielectric constant and tunability of Ba0.5Sr0.5TiO3–MgO–Mg2TiO4 composite ceramics increase and the Q × f values decrease. Ba0.5Sr0.5TiO3–Mg2TiO4–MgO composites have dielectric constant of 123.0–156.5 and tunability of 14.4–28.5 % at 10 kHz under 3.9 kV/mm, indicating that they are promising candidate materials for tunable microwave applications requiring a low dielectric constant.