Papers by Author: Jian Min Zhu

Abstract: In this work, 0.33BaTiO₃-0.67BiFeO₃ multiferroic ceramics doped with x mol% MnO₂ (x= 0.1-1.0) were fabricated by solid-state reaction method, and their microstructure and dielectric property were also investigated. The perovskite phase structure of the solid solutions was confirmed by X-ray diffraction patterns, and the formation of minor impure phase of Bi₂Fe₄O₉ was prevent effectively by Mn-doping. With increasing the Mn-doped concentration, the dielectric constants of Mn-doped 0.33BaTiO₃-0.67BiFeO₃ multiferroic ceramics first increased, and reached a maximum value of 340 (measured @1MHz) at the Mn-doped concentration of 0.60 mol%, and then decreased. On the other hand, the dielectric losses first decreased, and reached the minimum value at the Mn-doped concentration of 0.30 mol%, and then increased along with increasing the Mn-doped concentrations. The ferroelectric domain structures in the Mn-doped 0.33BaTiO₃ - 0.67BiFeO₃ multiferroic ceramics with rhombohedral symmetry were also revealed by TEM image and selected area electron diffraction patterns, and tweed-like domain structures were observed.

Abstract: BaTiO3 (BT) nanoparticles were prepared by the hydrothermal technique using different starting materials and the microstructure examined by XRD, SEM, TEM and HRTEM. X-ray diffraction and electron diffraction patterns showed that the nanoparticles were the cubic BaTiO3 phase. The BT nanoparticles prepared from the starting materials of as-prepared titanium hydroxide and barium hydroxide have spherical grain morphology, an average size of 65 nm and a fairly narrow size distribution. A uniform diffraction contrast across each single grain is observed in the TEM images, and the clear lattice fringes (with d110 = 0.28 nm) observed in HRTEM images reveal that well-crystallized BT nanoparticles are synthesized by the hydrothermal method. The edges of the particles are very smooth, with no surface steps. BT nanoparticles with average grain size of 90 nm, synthesized using barium hydroxide and titanium dioxide as the starting materials, show surface facets. In this case a bimodal size distribution of large faceted and smaller particles is observed. Diffraction contrast variation across the particles caused by high strains within the particles is clearly observed. The high strains obviously stem from structural defects formed during hydrothermal synthesis, presumable in the form of lattice OH− ions and their compensation by cation vacancies. HRTEM images demonstrate that surface facets parallel to the (100) and (110) planes and small islands with 3 ~ 4 atomic layer thickness are frequently observed around the edge of the particles.

Abstract: Chestnut-bur-like rutile titania assemblies are successfully synthesized by a sonochemical method. Scanning electron microscopy and transmission electron microscopy analyses reveal that the assemblies are formed by radial coagulation of rutile acicular nanocrystals. Effects of experimental conditions on the phase and structure of the products are also presented.

Abstract: By means of solid-state reactions method, ZnSnO3 nanoparticles were prepared in the reactions of ZnCl2 and SnCl4·5H2O with KOH in the presence of added KCl crystal, and were assembled into 3-D aggregates with tetragonal-like shape in the size range of 20-200 nm. The products were characterized by powder X-ray diffraction (XRD), and the microstructures of the samples were investigated by transmission electron microscope (TEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscope (HRTEM) in detail. Probable mechanisms for the formation of such tetragonal-like shape of ZnSnO3 3-D aggregates are proposed.