Search

SrTiO3 ceramics with trace amounts of ZrO2 additives were prepared via the solid state reaction route. The effects of ZrO2 concentrations on microstructures, dielectric and energy storage properties of SrTiO3 ceramics were investigated. The grain size of the ceramics decreases with increasing ZrO2 concentration. Dielectric relaxation behaviors were observed in dielectric loss versus temperature plots and studied by the measurements of the activation energies, which indicated the behaviors were due to the doubly ionized oxygen vacancies and the space-charge polarization. An energy density of 1.62J/cm³ and a breakdown strength of 289kV/cm were achieved for SrTiO3 ceramics with 0.4mol% ZrO2 addition, which were higher than those of pure SrTiO3 ceramics. [ABSTRACT FROM AUTHOR]

We report the discovery of a new class of nanowires with a star-shaped cross section. Unlike most nanowires, it shows a prominent regular reentrant surface profile. The electron diffraction and electron energy loss spectroscopy analyses indicate that the nanowire is composed of superhard boron suboxide (B6O). The fivefold symmetry of the star-shaped nanowire could be understood as a cyclic twinning structure. The crystallographic analysis further suggested that it could be a common occurrence in boron-rich compounds. Star-shaped nanowires with regular reentrant surfaces are attractive for applications in nanotechnology. [ABSTRACT FROM AUTHOR]

Dielectric film capacitors are considered as potential candidates for advanced power electronics technology due to their extremely high-power densities and outstanding mechanical and thermal stability, but the further improvement of energy storage density is still needed. Here, a strategy is proposed to enhance the energy storage properties by introducing nanoscale polarization regions into amorphous films, which can significantly improve the maximum polarization and maintain a high breakdown strength. The (1−x) BaTiO3-xBi(Ni0.5Zr0.5)O3 ((1−x)BT-xBNZ) thin films are fabricated by the sol– gel method and the amorphous films with nanoscale polarization regions are obtained by adjusting the preparation process. Consistent with the conjecture, amorphous phase and nanoscale polarization regions in the (1−x) BT-xBNZ films are clearly observed by electron diffraction. Results show that giant recoverable energy density of 103.7 J cm−3 with high energy efficiency of 88.3% are simultaneously achieved at 8.3 MV cm−1 in 0.92BT-0.08BNZ thin films. Furthermore, the 0.92BT-0.08BNZ thin film exhibits excellent thermal stability in a wide temperature range of 20–200°C, ΔWrec/Wrec20°C < 2.2%. This work provides a novel method for dielectric thin film capacitors applied in high temperature and electric field. [ABSTRACT FROM AUTHOR]

The structure, electrical properties, and depoling mechanism of the (0.95-x)BiScO3-xPbTiO3-0.05Pb(Zn1/3Nb2/3)O3 (BS-xPT-PZN, x=0.54-0.70) compositions close to the morphotropic phase boundary (MPB) have been systematically investigated as a function of PbTiO3 content (x). The phase approached from the rhombohedral toward the tetragonal phase when the PbTiO3 contents increased. The composition with high PT content exhibited normal ferroelectric behavior while it showed a diffused phase transition characteristic as PT decreased. In the vicinity of the MPB, the ceramics showed enhanced piezoelectric, electromechanical, and ferroelectric properties with piezoelectric constant d33=490 pC/N, planar electromechanical coupling factors kp=57.4%, remnant polarization Pr=40.1 μC/cm2, and coercive field Ec=28.5 kV/cm with a high transition temperature Tm∼417 °C, respectively. The thermal depoling experiments of the polarization for samples with different phase structures were investigated and the possible depoling mechanism was discussed. [ABSTRACT FROM AUTHOR]

Dielectric materials with large maximum polarization but small lossy hysteresis, high electrical breakdown, and postponed maximum polarization can store a large amount of electrical energy and are thus promising candidates for energy storage applications. In this work, a dielectric capacitor based on (Sr0.98Ca0.02)(Ti,Zr)O3 system achieved the elevated energy storage performances calculated from the polarization-electric field hysteresis loops due to enhanced breakdown strength by Zr substitution. Dielectric relaxation could be ascribed to the appearance of the doubly ionized oxygen vacancies verified by activation energy. For the studied system, dielectric breakdown dominated for the enhancement of energy storage performances because of the difference of ferroelectric activity and cation stability between Zr and Ti ions. The optimal Zr-modified composition exhibited better energy storage performances in contrast with pure (Sr0.98Ca0.02 )TiO3,suggesting that they might be an emerging candidate for next-generation high-energy devices. [ABSTRACT FROM AUTHOR]

Y-doped Ba1-xSrxTiO3 (Y-BST) ceramics (x = 0.1, 0.2, 0.4, 0.7) were prepared by solid-state reaction and sintered at 1250, 1300, 1350, and 1400 °C for 1 h. The effect of strontium solution and sintering temperature on the structure, microstructure and dielectric properties of Y-BST was investigated. SEM investigations revealed a grain size decreasing with the Sr content increase. The temperature dependence of permittivity showed decrease in phase transition temperature with higher Sr content. Enhancing sintering temperature is effective to increase the grain size and improve the microstructure porosity. The XRD patterns of all Y-doped Ba0.3Sr0.7TiO3 ceramics indicated that the crystal cell parameters increase when temperature increased. However, the (002) and (200) peaks of Y-doped Ba0.3Sr0.7TiO3 split when sintering temperature was increased to 1400 °C, which makes the structure of the specimen transit to tetragonal (a = 3.9857 Å and c = 4.018 Å) from cubic. It may be attributed to the fact that Y3+ ion can occupy both A site and B site of Ba0.3Sr0.7TiO3 sintered at 1400 °C, which leads to the large different internal stress in individual grains, and then induces the structure change. The temperature coefficient of capacitance (TCC) value of the Y-doped Ba0.3Sr0.7TiO3 sintered at 1400 °C changed little within ±6% over a temperature range from 10 to130 °C. [ABSTRACT FROM AUTHOR]

A steady nano organic-inorganic perovskite hybrid with [H23-AMP]3/2Fe(CN)6 (3-AMP = 3-methylaminopyridine) was prepared in the air. The structure is an unusual layered organic-inorganic type. The resulting hybrid enveloped in paraffin to prepare [H23-AMP]3/2Fe(CN)6 paste electrode (HPE) shows good electrochemical activity and a couple of oxidation and reduction peaks with potential of cyclic voltammometry (CV) at around 440mV and 30mV. Compared with that on CPE, oxidation potential of Fe(CN)63- on HPE shifts negatively 259.7mV and that of reduction shifts positively 338.7mV, which exhibits that [H23-AMP]3/2Fe(CN)6 can accelerate the electron-transfer to improve the electrochemical reaction reversibility. Such characteristics of [H23-AMP]3/2Fe(CN)6 have been employed to prepare the DNA biosensor. The single-strand DNA (ssDNA) and double-strand DNA (dsDNA) immobilized on HPE, respectively, can improve the square wave voltammometry (SWV) current and SWV potential shifts positively. The effect of pH was evaluated. And there is hybridization peak on SWV curve using HPE immobilized ssDNA in the complementary ssDNA solution. And HPE immobilized ssDNA can be utilized to monitor the DNA hybridization and detect complementary ssDNA, covering range from 3.24 × 10-7 to 6.72 × 10-5 g/mL with detection limit of 1.57 × 10-7 g/mL. The DNA biosensor exhibits a good stability and reproducibility. [ABSTRACT FROM AUTHOR]

Ba0.4Sr0.6TiO3 (BST) films were deposited on quartz substrates by radio frequency (RF) magnetron sputtering in O2/Ar atmosphere. The structural property of the film was studied by XRD, the morphology by AFM and the cross-section by SEM. As-grown films were amorphous and presented compacted grain morphology, its surface fluctuation was about 3 nm. When sputtering time was higher than or equal to 3 h, the annealing temperature above 550°C, the crystalline film has been identified as a cubic perovskite structure. When sputtering time was 5 h, the thickness of film was about 1 μm. Different thickness films could be obtained by controlling the sputtering time. [ABSTRACT FROM AUTHOR]

Sr(Ti0.95Zr0.05)O3 ceramic was sintered using xmol.% CTS (x=0, 0.5, 1.5, 4, 7) as sintering additive for the first time. Although Sr(Ti0.95Zr0.05)O3 ceramic could not be fully sintered even at 1420°C, the densification temperature could be decreased to 1280°C by using CTS, which begin melting when temperature reaches higher than 1150°C. The microstructures of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Apparent density and the dielectric properties were established at room temperature. The measuring frequency was 1MHz. The microstructure and dielectric properties greatly changed depending on the amount of CTS additive. The optimum concentration to obtain nicer dielectric properties was 0.5mol.%. [Copyright &y& Elsevier]

Cobalt-doped (1-x)BiScO3-xPbTiO3 piezoelectric ceramics were fabricated by conventional solid state synthesis, in which a morphotropic phase boundary (MPB) region was observed in the compositional range of 0.48≤x≤0.53 from the phase structure measurement. Co doping in the 0.50BiScO3–0.50PbTiO3 ceramics resulted in a relaxor ferroelectric behavior due to cation disorder. The ferroelectric phase transition of the composition x=0.50 near the MPB was found to be a displacive and first-order transition with excellent piezoelectric properties, Tm=470 °C, d33=282 pC/N, Kp=0.49, indicating a future high-temperature piezoelectric application [ABSTRACT FROM AUTHOR]