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xBa 0.7 Sr 0.3 TiO 3 -SrTiO 3 (BST-ST) multilayer ceramics with different BST layers (x=1, 3, 5) were designed and fabricated by lamination of Ba 0.7 Sr 0.3 TiO 3 (BST) and SrTiO 3 (ST) tapes. Dielectric and energy storage properties of the multilayer ceramics were investigated. BST-ST multilayer ceramics exhibited enhanced temperature- and frequency-stability of dielectric properties, accompanying high permittivity (~2000) and low dielectric loss (<0.005) at room temperature. P-E loops revealed that BST-ST multilayer ceramics displayed low remnant polarization and favorable maximum polarization. The optimal energy storage performance was obtained in the composition of x=5 with dielectric breakdown strength of 220 kV/cm and energy storage density of 2.3 J/cm 3 . These results indicate that BST-ST multilayer ceramics can be a favorable candidate for dielectric capacitor applications. [ABSTRACT FROM AUTHOR]

In this paper, a core-shell structure, where the BaTiO 3 (BT) particles were coated with 0.25Bi(Zn 1/2 Ti 1/2 )O 3 -0.75BaTiO 3 [BT@x(0.25BZT-0.75BT)] by sol-gel method, was fabricated and confirmed by transmission electron microscopy (TEM). The impedance data of BT, 0.25BZT-0.75BT and BT@x(0.25BZT-0.75BT) (x=0.5–1.0) ceramics was collected and fitted by different equivalent circuits. The core and shell regions of BT@x(0.25BZT-0.75BT) (x=0.5–1.0) ceramics can be separated in complex impedance plots (fitted by a 4RC equivalent circuit), according to the activation energies of BT and 0.25BZT-0.75BT. The calculated activation energy of the core part in BT@x(0.25BZT-0.75BT) ceramics is relatively stable, being closer to the activation energy (0.86 eV) of BT, while the activation energy of the shell was found to increase from 0.28 eV to 0.53 eV with increasing the shell thickness. The average core/shell ratio (d gc /d gs ) for BT@0.8(0.25BZT-0.75BT) ceramics was found to be on the order of 7.26, calculated by a modified two-layer dielectric model. In addition, Lichtenecker formula was used to simulate the dielectric constant of BT@0.8(0.25BZT-0.75BT) ceramics at room temperature and the simulated results are in agreement with the measured values. [ABSTRACT FROM AUTHOR]

Abstract: Effects of nonstoichiometric SrTiO3 ceramics have been investigated in the range of Sr/Ti=0.994–1.004. A cubic perovskite structure is maintained at all compositions without any secondary phase. Grain size increases at the beginning and then decreases with increasing Sr/Ti ratio. The highest breakdown strength and energy density are obtained at Sr/Ti=0.996, 283kV/cm and 1.21J/cm3, respectively, which are higher than that of stoichiometric SrTiO3 ceramic (210kV/cm of breakdown strength, 0.7J/cm3 of energy density). Sr/Ti>1 ST ceramics are prone to semi-conductivity process. Among them, the ST ceramic at Sr/Ti=1.004 has the highest permittivity, 2455. [Copyright &y& Elsevier]

Abstract: Nb2O5 and Nb–Co doped 0.85BaTiO3–0.15Bi(Mg1/2Ti1/2)O3 (0.85BT–0.15BMT) ceramics were investigated. From XRD patterns, undesired phase was observed when the (Nb2O5/Nb-Co) doping levels exceed 3wt.%/2wt.%, giving rise to the deteriorate dielectric constant. The 0.85BT–0.15BMT ceramics doped with 2wt.%Nb2O5 was found to possess a moderate dielectric constant (ɛ ∼1000) and low dielectric loss (tan δ =0.9%) at room temperature and 1kHz, showing flat dielectric behavior over the temperature range from −55 to 155°C. It was found that the formation of core–shell structure in the BT based ceramics is controlled by the doping sequence of Nb- and Bi-oxides. [Copyright &y& Elsevier]

Abstract: In this work, Na0.5Bi0.5TiO3 (NBT) was used to improve the high temperature dielectric properties of Nb, Co-doped BaTiO3 (BT). Different x was selected (x =0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.2, 0.3, 0.4) to optimize the ratio of BT to NBT in (1− x) BT–xNBT solid solution. The dielectric constant of the original X7R material is about 4900 at room temperature, decreasing to 2500 with NBT addition (x =0.2). Of important is that the temperature stability was improved with dielectric constant variation being less than ±15% up to 160°C. [Copyright &y& Elsevier]