Papers by Author: Jian Mei Xu

Abstract: BiFe _1-x Co_xO₃(x= 0-0.3) polycrystalline samples were prepared in order to study the effect of Co substitution on BiFeO₃ structural, magnetic and electric properties, which to the best of our knowledge, the related work has not been reported. The samples were synthesized by a simple solid-state method, which the process contains mortar grind, calcinate, press and sinter. The crystal structures were refined from XRD data in the acentric R3c space group; a second phase CoFe₂O₄ was identified, in increasing amounts with the increase of x. The magnetic moment is greatly improved and the magnetization for BiFe _0.96 Co _0.04 O₃ was found to be 0.756 emu/g.

Abstract: Undoped and antimony-doped tin oxide (ATO) thin films were prepared by sol-gel process in the solution of metal salts of tin (II) chloride dehydrate and antimony tri-chloride. The microstructure of the thin films was analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). Compared with undoped tin oxide, doped antimony tin oxide films coated glass substrate were homogeneous in composition and morphology after being sintered at different temperatures. Electrical behavior of the doped films was discussed in terms of sheet resistance measured by four point probe. From the experimental data, the sheet resistance of the films could be as low as 100-200Ω/□

Abstract: Antimony-doped tin oxide thin films have a range of technical applications as conductive coatings, and sol-gel processing seems to offer some advantages over other coating techniques. In this study, the sol was prepared by sol-gel approach from SnO2·H2O and SbCl3 in alcohol. It was found that the heat-treatment temperature and doping level have strong influences on the microstructure and composition of Sb: SnO2 films. The SnO2 crystals exist mainly as tetragonal rutile structure. The optimum heat-treatment temperature is about 450 ~ 500°C, and the film is composed with nanocrystals and nano-pores. Microstructure and the electrical behaviors of Sb-doped SnO2 thin films derived by sol-gel process were investigated.

Abstract: Using citric acid (CA) as a chelating agent, (1-x)Ca0.4Sm0.4TiO3 –xLi0.5Nd0.5TiO3 (CSLNT) (x = 0.3) ceramic powders were synthesized by the Pechini method. The CSLNT precursor and derived oxide powders were characterized by differential thermal analysis, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy. Only perovskite CSLNT (x=0.3) phase appeared when the CSLNT precursor was calcined at 1050°C for 3 h. Compared with the conventional solid-state reaction method, microwave dielectric ceramics with better properties could be prepared by the Pechini method at lower sintering temperature.

Abstract: The different amounts of manganese dioxide were doped to Ba4.5Sm9Ti18O54 (BST)ceramics. It was found that the doping sequence of Mn had serious influences on the microwave dielectric properties of the BST ceramics. When manganese dioxide was added before the mixtures were calcined, the dielectric properties of ceramics were poor and decreased with the increase of the Mn content. When the Mn content was between 2.0wt% and 3.0wt%, the BST ceramics had no microwave characteristic. But adding manganese dioxide in a range of 0.0 to 1.0wt% after the mixtures were calcined enhanced the microwave dielectric properties of the BST ceramics. When the Mn content changed from 0 to 1.0wt%, the microwave properties of the BST ceramics increased, but the microwave properties decreased while the Mn content was over 1.0wt%. The ceramics with 3.0wt% Mn content had also no microwave characteristic. The optimum microwave dielectric properties were as follows: εr=76, Q·f=7280,τf=-3.6ppm/k.