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Ba0.6Sr0.4TiO3-Mg2SiO4-MgO composite ceramics were prepared by a solid-state reaction method and their dielectric tunable characteristics were investigated for the potential application as microwave tunable materials. The addition of Mg2SiO4-MgO into Ba0.6Sr0.4TiO3 forms ferroelectric (Ba0.6Sr0.4TiO3)-dielectric (Mg2SiO4-MgO) composites and shifts the Curie temperature to a lower temperature. The dielectric constant and loss tangent of Ba0.6Sr0.4TiO3-Mg2SiO4- MgO composites have been decreased and the overall tunability is maintained at a sufficiently high level. The microwave dielectric properties of Ba0.6Sr0.4TiO3-Mg2SiO4-MgO composites were evaluated. Ba0.6Sr0.4TiO3-Mg2SiO4-MgO composites have tunability of 9.2 to 10.5% at 100 kHz under 2 kV/mm, indicating that it is a promising candidate material for tunable microwave applications requiring a low dielectric constant. [ABSTRACT FROM AUTHOR]

Ba0.6Sr0.4TiO3-La(B0.5Ti0.5)O3 (B = Mg, Zn) ceramics were prepared by a solid-state reaction method, and their microwave dielectric characteristics and tunability were investigated. The ferroelectric-dielectric solid solutions with cubic perovskite structures were obtained for compositions of 10 to 60 mol% La(Mg0.5Ti0.5)O3 and 10 to 50 mol% La(Zn0.5Ti0.5)O3. With the increase of linear oxide dielectric content, the dielectric constant and tunability were decreased and Qf was increased. Ba0.6Sr0.4TiO3-La(Mg0.5Ti0.5)O3 has better dielectric properties than Ba0.6Sr0.4TiO3-La(Zn0.5Ti0.5)O3. 0.9Ba0.6Sr0.4TiO3-0.1La(Mg0.5Ti0.5)O3 has a dielectric constant ϵ = 338.2, Qf = 979 GHz and a tunability of was 3.7% at 100 kHz under 1.67 kV/mm. The Qf value of 0.5Ba0.6Sr0.4TiO3- 0.5La(Mg0.5Ti0.5)O3 reached 9367 GHz, but the tunable properties were lost. [ABSTRACT FROM AUTHOR]

Ba0.6Sr0.4TiO3-Sr(Ga0.5Ta0.5)O3 solid solutions are prepared by a solid-state reaction method, and their dielectric and tunable characteristics are investigated. The solid solutions with cubic perovskite structures are obtained for compositions of 10-50 mol% Sr(Ga0.5Ta0.5)O3. It is observed that the addition of Sr(Ga0.5Ta0.5)O3 into Ba0.6Sr0.4TiO3 causes a shift in the phase transition peak to a lower temperature. Ba0.6Sr0.4TiO3-Sr(Ga0.5Ta0.5)O3 solid solutions exhibit depressed and broadened phase transition peaks, resulting in decreased dielectric constants and dielectric losses at room temperature. With the increase of Sr(Ga0.5Ta0.5)O3 content, the dielectric constant, loss tangent, and tunability are decreased. 0.9Ba0.6Sr0.4TiO3-0.1Sr(Ga0.5Ta0.5)03 has a dielectric constant ϵ = 534 and a tunability of 16% at 100 kHz under 2.63 kV/mm. The dielectric characteristics of Ba0.6Sr0.4TiO3-Sr(Ga0.5Ta0.5) O3 ceramics at microwave frequencies are also evaluated. [ABSTRACT FROM AUTHOR]