Papers by Keyword: SrBi₂Nb₂O₉

Abstract: Ferroelectric ceramics, Sr_1-xLa_xBi₂Nb_2-x/5O₉ (SLBNO), were prepared using the conventional solid-state reaction method. Effect of lanthanum substitution on dielectric and ferroelectric properties of SrBi₂Nb₂O₉ (SBN) ceramics were investigated. X-ray diffraction analyses (XRD) revealed that all the specimens had a single phase with orthorhombic space group A2₁am. The maximum dielectric permittivity peak broadened gradually with the increase in lanthanum substitution indicated that the phase transition from normal ferroelectrics to relaxor ferroelectrics occurred in SLBNO ceramics. The modified Curie-Weiss (CW) law was used to describe the relaxor behavior of the SLBNO ceramics. The relaxation indication coefficient (γ) was estimated from a quadratic fit of modified CW law and was found to be 1.7 and 2.0 for the SLBN20 and SLBN30 specimens, respectively. Curie temperature (T_c) of the SBN ceramic was decreased gradually with the increase in lanthanum substitution. In addition, the ferroelectric properties of the SBN ceramic were enhanced significantly by the introduction of lanthanum ions and the maximum of remnant polarization (P_r) was found to be 4.35 μC/cm² for the SLCB20 specimen. Nature of relaxor behavior of the SLBNO ceramic is attributed to the cationic disordering at nanoscale on A site by the introduction of lanthanum ions.

Abstract: In this paper SrBi2Nb2O9 was prepared by molten salt synthesis method and KCl chosen as molten medium. In order to disclose possible formation mechanism of SrBi2Nb2O9, a simple route was established for comparison by dividing the starting precursors into four groups. With the help of XRD, possible synthesis route was analyzed. The results showed that pure SrBi2Nb2O9 powders could be obtained at temperature higher than 700oC by molten salt synthesis. Intense synthesis reaction happened in the temperature range from 500 to 700oC. The reaction mechanisms of SrBi2Nb2O9 included four steps, namely the formation of 1) SrBi2O4 at close to 600oC,2) BiNbO4 from the reaction of at 600-700 oC, 3) SrBi2Nb2O9 from the reaction of SrBi2O4 and Nb2O5 and 4)SrBi2Nb2O9 from the reaction of BiNbO4 and SrCO3. The molten salt could improve distribution and reactivity of the precursors and significant formation of SrBi2Nb2O9.

Abstract: SrBi2Nb2O9 (SBN) thin films were prepared on fused quartz substrates at room temperature by pulsed laser deposition. The crystallization behavior and surface morphology were studied at various oxygen pressures by XRD and AFM. The results indicated that the films had polycrystalline structure with a single layered perovskite phase, and exhibited higher crystalline quality, less rough surface morphology, and larger grain size with increasing oxygen pressure. The optical transmittance of the samples was measured in the wavelength range 200-900 nm, and the dispersion relation of refractive indices and wavelength was found to follow the single electron oscillation model. The energy gap of SBN films grown at oxygen pressure of 5 Pa was estimated to be around 3.88 eV by assuming a direct transition between valence and conduction bands.

Abstract: Well-crystallized SrBi2Nb2O9 (SBN) thin films with good surface morphology were fabricated on quartz glass substrates by RF magnetron sputtering technique at a deposition temperature of 600°C under the O2/Ar(3:1) pressure of 2.4 Pa for 2 hour. The films exhibited bismuth-layered perovskite phase structure without pyrochlore phase and the ratio of Sr:Bi:Nb is about 1:1.92:1.98. The nonlinear optical properties of the films were determined by a single beam Z-scan technique at a wavelength of 532 nm with laser duration of 25 ps. The measured values of the real and imaginary parts of the third-order nonlinear optical susceptibility were 4.324×10-8esu and 1.278×10-8esu, respectively. The large nonlinear optical effect shows that the SrBi2Nb2O9 thin films have great potential application in designing nonlinear optical devices.

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.