We investigated the structure, dielectric properties and energy density performances of cubic perovskite-structured Mg-doped SrTiO3 ceramics that were prepared by the solid-state reaction method. SrTiO3 ceramic exhibited a relatively stable permittivity about 265–290 and enhanced dielectric breakdown strength (DBS) by Mg isovalent doping. Doping effects on the energy-storage properties in SrTiO3 ceramics was performed by complex impedance analysis and polarization–electric field hysteresis loops. The energy storage density was dependent on DBS while energy efficiency was closely related to the remnant polarization. The possible physical mechanisms, including grain, gain boundary and interfacial polarization effects, were discussed to explain the improvement of dielectric breakdown strength. The bulk Mg-doped SrTiO3 materials have shown interesting energy densities (1.86 J/cm3) with good energy storage efficiency (about 89.3%) indicating that they can be a promising candidate for high energy density capacitor applications.

•Develop a new low-cost Bi-based high temperature piezoceramics with Tc∼580 °C.•La can drive the changes of phase structure and electrical characterization.•La-driven compositions exhibit improved electrical properties.•Thermal stability is closely related to domain type of ferroelectric ceramics.La-doped 0.3(Bi1−xLax)(Zn0.5Ti0.5)O3-0.7PbTiO3 (BLZT-PT) ceramics with 0 ≤ x ≤ 0.30 was studied. La doping reduced the tetragonality/polar distortion, shifted Curie temperature, changed thermal stability and improved ferro-piezoelectric properties of the ceramics. The sample with optimal composition at x = 0.055 exhibited high Curie temperature of about 580 °C with good piezoelectric properties. This makes BLZT-PT a promising candidate for next-generation of piezoelectric ceramics at high-temperatures.Download high-res image (144KB)Download full-size image

The dielectric properties of SrTiO3 ceramics sintered in nitrogen (N2) exhibit a weak temperature- and frequency-dependent giant permittivity (>104) as well as a very low dielectric loss (mostly < 0.02) over a broad temperature range from −100 to 200 °C. Based on the results of ac conductivity and structural analysis, the giant permittivity and low dielectric loss were due to the fully ionized oxygen vacancies and giant defect-dipoles. When further sintering these ceramics in air, the materials exhibit a large temperature- and frequency-dependent high dielectric loss, which were due to the ionization and motion of oxygen vacancies.

Ceramic samples of xBi(Al0.5Fe0.5)O3–(1 − x)PbTiO3 (BAF-PT, x = 0.05–0.5) solid solutions were fabricated using the conventional solid state reaction method. X-ray diffraction analysis revealed that all compositions can form single perovskite phase with tetragonal symmetry. The relationship between the tetragonal lattice parameters, tetragonality c/a, cell volume, and ferro-piezoelectric characterization as a function of x was systematically investigated. The BAF modification can effectively improve the poling condition at a proper BAF content. A combination of piezoelectric constant of d33 (50–60 pC/N), electromechanical planar coupling coefficients of kp (20.3–22.5%), and high Curie temperature Tc (>478 °C) suggested that BAF–PT could be a good candidate for high-temperature piezoelectric applications.Highlights► Low-cost Bi-based high temperature piezoceramics. ► A new high temperature system with Curie point >478 °C, compared to BiScO3–PbTiO3 (450 °C). ► Effectively improve the poling conditions.

The effects of Nb doping on the microstructures and electrical properties of 0.44Bi(Sc0.75Co0.25)O3–0.56PbTiO3 piezoelectric system were investigated. Our results indicate that a small amount of Nb ions can result in phase transition and improve the electrical properties. Enhanced ferroelectric–piezoelectric properties are obtained at low-level doping content with a slight reduction of transition temperature. The composition doped with 0.5 mol% Nb ions shows the optimal electrical properties with piezoelectric constant d33 = 390 pC/N, planar electromechanical coupling factor kp = 0.51, and a high transition temperature ∼351 °C, indicating a promising candidate for high-temperature applications.