Structure Refinement, Dielectric and Ferroelectric Properties of Crystalline (BaxSr1-x)Bi₂Ta₂O₉

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We synthesized a series of (Ca,Ba)-layered compounds (Ba x Sr 1- x )Bi 2 Ta 2 O 9 ( x =0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) by a solid-state reaction, and examined the structures, and the dielectric and ferroelectric properties. Structural analysis by X-ray diffraction (XRD) revealed that the structures of (Ba x Sr 1- x )Bi 2 Ta 2 O 9 for 0.0≤ x ≤0.4 are orthorhombic with A 2 1 a m symmetry, whereas those of (Ba x Sr 1- x )Bi 2 Ta 2 O 9 for 0.6≤ x ≤1.0 are tetragonal ( I 4/ m m m ). The temperature dependence of ε r ' and tan δ were investigated in detail for various frequencies and compositions. We observed that the dielectric constant ε r ', tan δ, T c , and hysteresis loop were strongly influenced by from Sr 2+ to Ba 2+ .