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Lead-free [(Bi0.5Na0.5)0.94Ba0.06]1-xLaxTiO3 (BNBT-xLa) ceramics with x = 0, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 mol.% were synthesized by the solid-state combustion technique with calcination and sintering temperatures of 750 °C and 1150 °C, respectively, for 2 h. The phase formation, microstructure, dielectric, ferroelectric and energy storage properties of the BNBT-xLa ceramics were investigated. The XRD patterns of the powders showed a pure perovskite phase for all samples. The average particle size increased from 298 to 379 nm with increasing x. All ceramics showed coexisting rhombohedral and tetragonal phases. When x rose, the content of the tetragonal phase increased, as validated by the Rietveld refinement method. The average grain size decreased from 1.43 to 0.81 µm when x increased from 0 to 0.05 and then started to increase. The Curie temperature (Td) of the samples shifted to lower temperatures with rising x, owing to an increased tetragonal phase. The maximum dielectric constant (εm), remanent polarization (Pr) and coercive field (Ec) decreased with increasing x. The BNBT-0.05La ceramic exhibited the smallest grain size, and lowest Pr = 0.8 µC/cm2 and Ec = 2.9 kV/cm, with the highest energy storage efficiency (η ∼ 78.31%) and a large effective energy storage density (W ∼ 0.83 J/cm3) measured in an electric field of 80 kV/cm. [ABSTRACT FROM AUTHOR]

The (1-x)Mg0.7Zn0.3Fe2O4 – (x)Ba0.7Sr0.3TiO3 composites with x = 0.40, 0.50 and 0.60 were prepared by solid state reaction under two step sintering. Two step sintering conditions were determined by the first step (T1) at 1350 °C for holding time of 60 min and cooled down to the second sintering temperature (T2) with different temperatures between 900 and 1100 °C for holding time of 5 h. The sample with high percentage of shrinkage and dense ceramic was obtained from 0.4Mg0.7Zn0.3Fe2O4-0.6Ba0.7Sr0.3TiO3 with sintering of T2 at 1100 °C. XRD pattern showed combination of ferrite phase (Mg0.7Zn0.3Fe2O4) and ferroelectric phase (Ba0.7Sr0.3TiO3) and secondary phase of ZnO. Rietveld analysis confirmed main phases of Mg0.7Zn0.3Fe2O4 and Ba0.7Sr0.3TiO3, including MgFe2O4 and ZnO as secondary phase. It was found that the unit cell volume of Ba0.7Sr0.3TiO3 was smaller than Mg0.7Zn0.3Fe2O4 unit cell volume. Therefore, the short distance between ions of Ba0.7Sr0.3TiO3 phase produced the dense composites with increasing ferroelectric phase contents. The average grain size of ceramic was in the range of 0.74–1.07 µm with grain square shape in Mg0.7Zn0.3Fe2O4 phase and the average grain size of 0.59–0.70 µm with round oval shape in Ba0.7Sr0.3TiO3 phase. The dielectric constant was between 0.8 × 103 and 5.4 × 103 in the temperature range of 275 °C − 360 °C. The highest dielectric constant was obtained from 0.6Mg0.7Zn0.3Fe2O4−0.4Ba0.7Sr0.3TiO3 with T1 at 1350 °C with holding time for 60 min and T2 at 900 °C with holding time for 5 h. The hysteresis measurement was carried out to determine saturation magnetization, remanent magnetization and coercivity of the composites. The results revealed that higher concentration of ferrite led to optimal magnetic properties. [ABSTRACT FROM AUTHOR]

(1-x)Mg0.7Zn0.3Fe2O4-(x)Ba0.7Sr0.3TiO3ceramics composite with x = 0.0, 0.2, 0.4, 0.6 and 1.0 were prepared by the solid state reaction method. The spinel structure of the ferrite phase and perovskite structure of ferroelectric phase were confirmed by x-ray diffraction (XRD). SEM micrographs reveal compatibility of ferrite grains with ferroelectric grains. It can be seen size of grain decrease with increase Ba0.7Sr0.3TiO3phase concentrations. The magnetic property can be identified from the magnetic permeability of the sample and the values were observed to be 0.53–0.83 N/A2and its increases with the increasing of Mg0.7Zn0.3Fe2O4phase contents. The electrical resistivity values were found to be in the range ∼0.06–52.99 MΩm. The dielectric constant was determined as a function of frequency (in the range 100–104Hz). The results also reveal that for the lower concentrations of Mg0.7Zn0.3Fe2O4, ferroelectric behavior is noticed with a high electrical resistivity and dielectric constant. [ABSTRACT FROM AUTHOR]