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Dense (1− x)Ca(Mg1/3Ta2/3)O3/ xCaTiO3 ceramics (0.1≤ x≤0.9) were prepared by a solid-state reaction process. The crystal structures and microstructures were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Single-phase solid solutions were obtained in the entire composition range. Long-range 1:2 ordering of B-site cations and oxygen octahedra tilting lead to the monoclinic symmetry with space group P21/ c for x=0.1. For x above 0.1, the long-range ordering was destroyed and the crystal structure became the orthorhombic with space group Pbnm. The microwave dielectric properties showed a strong dependence on the composition and microstructure. The dielectric constant and temperature coefficient of resonant frequency increased nonlinearly as the CaTiO3 content increased while the Qf values decreased approximately linearly. Good combination of microwave dielectric properties was obtained at x=0.45, where ℇr=45.1, Qf=34 800 GHz, and τf=17.4 ppm/°C. [ABSTRACT FROM AUTHOR]

The dielectric characteristics of BaBi2Nb2O9, BaBi4Ti4O15, BaBi8Ti7O27, and La-substituted SrBi4Ti4O4 were investigated to discuss their ferroelectric phase transition and relaxor behaviors. BaBi2Nb2O9 showed typical relaxor behaviors, and a shift of Tm with increasing frequency was observed in BaBi4Ti4O15 and SrBi4− xLa xTi4O15 ( x=0.8, 1.0) but they underwent a real paraelectric–ferroelectric phase transition on zero-field cooling, while BaBi8Ti7O27 showed a normal ferroelectric nature. The reduced concentration and weakened coupling of the dipoles related to A-site bismuth are believed to be responsible for the appearance of short-range electric ordering and the relaxor behaviors in these bismuth layer-structured compounds. [ABSTRACT FROM AUTHOR]

The dielectric characteristics of BaBi2Nb2O9, BaBi4Ti4O15, BaBi8Ti7O27, and La-substituted SrBi4Ti4O4 were investigated to discuss their ferroelectric phase transition and relaxor behaviors. BaBi2Nb2O9 showed typical relaxor behaviors, and a shift of Tm with increasing frequency was observed in BaBi4Ti4O15 and SrBi4− xLa xTi4O15 ( x=0.8, 1.0) but they underwent a real paraelectric–ferroelectric phase transition on zero-field cooling, while BaBi8Ti7O27 showed a normal ferroelectric nature. The reduced concentration and weakened coupling of the dipoles related to A-site bismuth are believed to be responsible for the appearance of short-range electric ordering and the relaxor behaviors in these bismuth layer-structured compounds. [ABSTRACT FROM AUTHOR]