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Preparation of (Bi0.5Na0.5)1-xSrxTiO3 (BNST) ceramics with varying x to 0.1, 0.2 and 0.3 was conducted using solid-state method. The perovskite structure of BNST is observed for all compositions. The high dielectric constant (4000) at 100 kHz with high polarization (24 µC cm−2) of the prepared BNST ceramic has been obtained where high discharge energy density (0.843 J cm−3) at 40 kV cm−1 is achieved. The relaxor phenomenon of BNST ceramics also studied related to Sr content. All the prepared BNST ceramics have a γ greater than 1.6, which confirms that they behave as a relaxor ferroelectrics. [ABSTRACT FROM AUTHOR]

When the contributions of dipole and soften vibration mode are assigned to a complex impermeability and a real impermeability, respectively, the total complex permeability with frequency can be derived to modify the classical Landau-Devonshire theory. In a gaussian distribution and a skewed gaussian distribution of Curie temperature of second-order phase transition, the functions derived have the form of dispersion behavior of relaxor ferroelectrics. By comparing with experiment result, slight deviations appear on the two sides of peak of permittivity for the gaussian distribution, and improved by the skewed gaussian distribution. The relevant problems to be solved are proposed. [ABSTRACT FROM PUBLISHER]

BaTiO3 ceramics doped with 0.40 mol% NaNbO3 were prepared using a traditional approach by sintering at temperature of 1250 °C to 1290 °C. The prepared ceramics was characterized by very good dielectric properties, such as high dielectric constant (1.5 × 105), low dielectric loss (0.1), and good dielectric temperature stability in the −40 °C to 100 °C range for the sample sintered below 1270 °C. The dielectric characteristics obtained with XPS confirmed that Ti4+ ions remain in the state without any change. The huge increase in dielectric constant in NaNbO3 doped BaTiO3 samples occurs when large amount of Ba2+ ions are excited to a high energy bound state of Ba2+ − e or Ba+ to create electron hopping conduction. For samples with the content of NaNbO3 higher than 0.40 mol%, or sintering temperature higher than 1280 °C, compensation effect is dominated by cation vacancies with sharply decreasing dielectric constant and increased dielectric loss. The polaron effect is used to explain the relevant mechanism of giant dielectric constant appearing in the ferroelectric phase. [ABSTRACT FROM AUTHOR]