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The presence of 180° ferroelectric domains in polycrystalline BaTiO3 thin films has been observed with the aid of transmission electron microscopy. The 180° domain boundary exhibited a curved appearance, and its orientational relationship was demonstrated. It was found that equiaxial grains did not have 180° domain boundaries due to their higher boundary energy. The grain size effect on dielectric constant of polycrystalline BaTiO3 thin films was also discussed in conjunction with 180° ferroelectric domains.

Microstructural characteristics such as second phases, defect types and order structure were investigated in Ba(Mg1/3Ta2/3)O3 [BMT] ceramics using X-ray powder diffraction, scanning electron microscopy, wavelength-dispersive spectroscopy, and transmission electron microscopy. Two types of second phases having higher and lower Ba/Ta ratio compared to stoichiometric BMT, maybe exist in calcined powder of BMT. While one of them was consumed during sintering for 2 h, the other was remained after sintering. These results were discussed in terms of probable defect types in matrix of BMT. The presence and change of specific defect types can be correlated with the contribution of specific defect types to sintering behavior. Theoretical intensity of (100) superlattice reflection and saturated order parameter was also discussed. The microwave dielectric properties of sintered samples was discussed in terms of the presence of second phase and thus related defects types.

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Microwave dielectric properties of the solid solution between Ba(Ni1/3Nb2/3)O3 and Ba(Zn1/3Nb2/3)O3 were investigated. Samples were prepared by the conventional mixed oxide method as well as the Pechini method. Sintered samples were analyzed using x-ray diffraction and scanning electron microscopy, and their microwave dielectric properties were measured by the post resonator method. The sample prepared by the Pechini method revealed excellent dielectric properties, i.e., permittivity of 35.6, quality factor of 5700 at 10 GHz, and very small temperature coefficient of resonant frequency. Order-disorder behavior of this solid solution system was found to depend on processing parameters. Variation in microwave dielectric properties was discussed in terms of the order-disorder behavior, chemical composition, mixture rule, etc.