Papers by Keyword: SrBi₂Ta₂O₉

Abstract: In this study, ferroelectric thin films of SrBi2Ta2O9 (SBT) or bilayered SrBi2Ta2O9/ Ba(Zr0.1Ti0.9)O3 (SBT/BZT) are successfully deposited on Si substrate under the optimal RF magnetron sputtering conditions, and their electrical and ferroelectric characteristics are discussed. Ferroelectric thin films are deposited on Si substrate under the RF power of 80 W, chamber pressure of 10 mTorr, substrate temperature of 550oC, and different oxygen concentrations. The surface morphology of deposited thin films is observed from the FESEM images, and the memory windows and leakage current of the Al/SBT/BZT/Si (MFS) structure are measured by an impendence phase analyzer and a semiconductor parameter analyzer, respectively. The memory window, capacitance and leakage current density of MFS structures under different oxygen concentrations are also reported. We find that the memory window of bilayered SBT/BZT structure shows larger than one of single layer SBT structure.

Abstract: The microstructure and ferroelectric domains of SrBi2Ta1.6Nb0.4O9 ceramics were investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) equipped with energy dispersive spectroscopy (EDS). The X-ray diffraction patterns show that the lattice constants a and b decrease, and c increases by doping with Nb into SBT sample. Accordingly, it has large strain and lattice distortion in the lattice This suggests that the Nb atoms partially occupy the location of the Ta atoms in the lattice. From TEM observations, the grains show (008) preferred orientations in the sample, which agrees well with the XRD results. The 90° domain walls are identified by the 90° rotation relationship of the electron diffraction pattern about the [001] zone axis. The 180° domain walls and anti-phase boundaries (APBs) in Nb-doped SBT ceramics are also observed, which are irregularly shaped and highly curved. The traditional α-fringes can be found in the Nb-doped SBT ceramics, which are the evidence of large strains in the lattice.

Abstract: In this research, SrBi2+xTa2O9 (SBT) powders with different Bi content were prepared using conventional solid-state reaction method. The SrBi2+xTa2O9 ceramics (x=0 ,0.2 ,0.4 ,0.6) were fabricated by the cold isostatic compaction and sintering in the air. Microstructure and dielectric, ferroelectric properties of SBT ceramics were investigated by XRD, SEM, EDAX and dielectric tester. The effects of Bi content on dielectric, ferroelectrc properties in SBT ceramics were discussed.

Abstract: Thermal analysis and Raman spectra were carried out in SrBi2Ta2O9 (SBT) nanoparticles to investigate phase transitions. Two anomalies have been observed in temperature dependence of specific heat for SBT nanoparticles. Under the combination with Raman spectra, it indicates that there exists a new ferroelectric intermediate phase in the phase-transition sequence. So we can conclude that the phase-transition sequence in SBT nanoparticles should be ferroelectric-ferroelectric-paraelectric. Moreover, the size effect was discussed in consideration of inner compressive stress in nanoparticles for this special transition behavior. The calculated results show that the SBT nanoparticles keep the ferroelectricity until the particle size is decreased to 4.2 nm.

Abstract: A liquid source misted chemical vapor deposition (LSMCVD) system was used to deposit SrBi2Ta2O9 ferroelectric thin films on Pt/TiO2/SiO2/Si substrates using strontium nitrate, bismuth nitrate and fluorine tantalum acid as the starting ingredients. Citric acid, ethylene glycol, and ethylenediaminetetraacctic acid were employed as chelating agents to form homogeneous and stable sol. A density, homogenous, crack-free and c-axis oriented SrBi2Ta2O9 thin films were prepared successfully and the resultant thin film exhibits the ferroelectric properties of 2Pr of 3.8 C/cm2, 2Ec of 60kV/cm at ±3.5 V, respectively.

Abstract: The dielectric, ferroelectric and piezoelectric properties of strontium bismuth tantalate niobate, Sr1-xBi2+xTa2-yNbyO9 [SBTN10x(y)] ceramics were investigated. The samples were fabricated by a conventional ceramic fabrication technique. Curie temperature, Tc, increased with an increase in Nb concentration y, and Tc of SBTN2(y) showed two regions with different slopes that divided near y=1.0. The coercive field, Ec, of SBTN2(y) increased with the increase in y and the highest Ec of 90 kV/cm was obtained. SBTN2(0.6) and SBTN2(1.0) showed the highest coupling factor k33 of 0.17 in the SBTN2(x) system.