Study of Barium Bismuth Titanate Prepared by Mechanochemical Synthesis

Barium-bismuth titanate, BaBi4Ti4O15 (BBT), a member of Aurivillius bismuth-based layer-structure perovskites, was prepared from stoichiometric amounts of barium titanate and bismuth titanate obtained via mechanochemical synthesis. Mechanochemical synthesis was performed in air atmosphere in a planetary ball mill. The reaction mechanism of BaBi4Ti4O15 and the preparation and characteristics of BBT ceramic powders were studied using XRD, Raman spectroscopy, particle analysis and SEM. The Bi-layered perovskite structure Of BaBi4Ti4O15 ceramic forms at 1100 degrees C for 4 h without a pre-calcination step. The microstructure of BaBi4Ti4O15 exhibits plate-like grains typical for the Bi-layered structured material and spherical and polygonal grains. The Ba2+ addition leads to changes in the microstructure development, particularly in the change of the average grain size

Characterization of Barium Titanate Ceramic Powders by Raman Spectroscopy

Barium titanate, BaTiO3 ceramic powders were prepared by mechanochemical synthesis and by the Pechini method. A powder mixture of BaO and TiO2 was treated in a planetary ball mill in an air atmosphere for Lip to 1 h, using zirconium oxide vial and zirconium oxide balls as the milling medium. After 60 min BaTiO3 phase was formed. In both ways BaTiO3 ceramics were sintered after 2 h on 1300 degrees C without pre-calcinations step. The heating rate was 10 degrees C min(-1). The formation of phase and crystal structure of BaTiO3 was approved by X-ray diffraction analysis and the Raman spectroscopy. The morphology and microstructure of obtained powders were examined by scanning electron microscopy method. Sharp phase transition from ferroelectric to paraelectric state was observed. The hysteresis loop is very well performed with regular sharp characteristic of ferroelectric materials

Structure study of nanosized La- and Sb-doped BaTiO3

Lanthanum and antimony doped barium titanate powders were prepared by polymeric precursors method through Pechini process. Obtained powder was pressed into pellet and sintering was performed at 1300 degrees C for 8 h. The formation of phase and crystal structure of BaTiO3 was carried out by XRD analysis, Raman and IR spectroscopy. Microstructure properties such as grain size distribution and morphology of sintered samples were determined using scanning electron microscope. Therefore, it was analyzed relation between grain size, structure and properties of obtained ceramics. Influence of La- and Sb-doping on barium titanate properties was discussed. Crow

Impedance spectroscopy of nanocrystalline MgFe2O4 and MnFe2O4 ferrite ceramics: Effect of grain boundaries on the electrical properties

Two ferrite ceramic materials, MgFe2O4 and MnFe2O4, were successfully fabricated by a conventional sintering of nanosized powders (at 1373 K for 2 h) synthesized by soft mechanochemical route. The particle size and morphology of powders were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD analysis was carried out for the determination of phase purity, crystal structure and average crystallite size of sintered ferrites. Both mechanosynthesized ferrite samples show mean crystallite sizes in the nm-range. Over the frequency range of 100 Hz to 1 MHz, impedance spectra of prepared ferrite ceramics are investigated at and above room temperature. Changes in the impedance plane plots with temperature have been discussed and correlated to the microstructure of materials. An equivalent circuit model is applied to explore the electrical parameters (resistance and capacitance) associated with grains and grain boundaries. Complex impedance analysis indicates the dominance of grain boundary effects which control the overall electrical behaviour of studied ferrites. The decrease in grain boundary resistance with temperature suggests a thermally activated conduction mechanism. [Projekat Ministarstva nauke Republike Srbije, br. III43008 i br. III45003

Study on bi-layered ceramics powders prepared by the mechanochemical synthesis

Bi-layered structured ferroelectric materials-bismuth titanate, Bi4Ti3O12 (BIT) and barium-bismuth titanate, BaBi4Ti4O15 (BBT) powders were prepared by homogenization and sintering of mixture of stehiometric quantities of bismuth titanate and barium titanate obtained via mechanochemical synthesis. The Bi4Ti3O12 ceramic was obtained at 1000 degrees C for 4 h and BaBi4Ti4O15 ceramic at 1100 degrees C for 4 h. The phase formation and properties of Bi4Ti3O12 and BaBi4Ti4O15 were studied using XRD, Raman spectroscopy, EDS and SEM. Microstructure of Bi4Ti3O12 and BaBi4Ti4O15 exhibits plate-like grains typical for the bi-layered structured material. The Ba2+ addition leads to the change in the microstructure development, particularly in the change of the average grain size. Crow

Spectroscopic characterization of YAG and Nd:YAG single crystals

In this paper, we used the Czochralski method to obtain good quality yttrium aluminium garnet (YAG, Y3Al5O12) and yttrium aluminium garnet doped with neodymium (Nd: YAG) crystals. The investigations were based on the growth mechanisms and the shape of the liquid/solid interface crystallization front on the crystal properties and incorporation of Nd3+ ions. The obtained single YAG and Nd: YAG crystals were studied by use of x-ray diffraction, Raman and IR spectroscopy. There are strong metal oxygen vibrations in the region of 650-800 cm(-1) which are characteristics of Al-O bond: peaks at 784/854, 719/763 and 691/707 cm(-1) correspond to asymmetric stretching vibrations in tetrahedral arrangement. Peaks at 566/582, 510/547 and 477/505 cm(-1) are asymmetric stretching vibrations and 453/483 cm(-1) is the symmetric vibration of the Al-O bond in octahedral arrangements of the garnet structure. Lower energy peaks correspond to translation and vibration of cations in different coordinations-tetrahedral, octahedral and dodecahedral in the case of the lowest modes

Raman spectroscopy study of anodic film on Ag43Cu37Zn20 alloy

The objective of this study was characterization of anodic film obtained when Ag43Cu37Zn20 alloy was treated electrochemically in 3.5% wt. NaCI under potentiostatic conditions. At the potential of +0.25 V a complex multilayer film is formed. XRD shows that it consists of CuCI and zinc hydroxichlorides with a small amount of Cu2O, probably formed in the film pores. The anodic film is a mixture of Cu2O, CuCI, Zn-5(OH)(8)center dot H2O and beta-Zn(OH)Cl. Phases of the alloy, Ag and Cu rich, show different anodic behavior. It was assumed that all phonon lines in the obtained Raman spectra were of the Lorentzian type, which is one of the common type of lines for this kind of analysis. Phases of Ag, CuCI, fl-Zn(OH)CI, Cu2O and Zn-5(OH)(8)(Cl)(2)center dot H2O were all registered by XRD

Infrared and Raman spectroscopy study of antimony doped barium titanate prepared from organometallic complex

Pure and antimony doped barium titanate powders were prepared by polymeric precursors method through Pechini process, which was carried out as a three-stage process from organometallic complex. Obtained powder was pressed into pellets and sintering was performed at 1300 degrees C for 8 h with heating rate of 10 degrees C min(-1). The formation of phase and crystal structure of pure and Sb-doped barium titanate was approved by XRD analysis, Raman and IR spectroscopy. The influence of Sb doping on microstructure of barium titanate ceramics was investigated by scanning electron microscopy. Therefore, the relation between grain size, structure and properties of the obtained ceramics was analyzed. Influence of Sb doping on barium titanate properties was discussed

Spectroscopy study of Bi12GeO20 single crystals

In this work single crystals of bismuth germanium oxide (Bi12GeO20) have been grown by the Czochralski method. Growth conditions were studied. The critical diameter and the critical rate of rotation were calculated. Suitable polishing and etching solutions were determined. The structure of the Bi12GeO20 has been investigated by X-ray diffraction, Raman and FTIR spectroscopy. The obtained results are discussed and compared with published data. On the basis of the measurements by Raman spectroscopy, we observed 15 modes

The characterization of the barium titanate ceramic powders prepared by the Pechini type reaction route and mechanically assisted synthesis

BaTiO3 ceramic powders were prepared by a complex method based on the Pechini type reaction route and mechanically assisted synthesis. In both ways BaTiO3 ceramics were sintered after 120 min on 1300 degrees C without pre-calcination steps. The crystal structure was investigated by the XRD, IR and Raman spectroscopy. The particle size and morphology of BaTiO3 were examined by XRD and SEM. The XRD results of powders indicate the formation of cubic phase of BaTiO3. It can be observed that in the case of Pechini process BaTiO3 powder is well crystallized but in the case of mechanochemistry process, significant amount of amorphous phase was detected. The sintered BaTiO3 ceramic sample prepared by Pechini process, shows the formation of tetragonal phase. However, IR and Raman spectrum showed a mixture of cubic and tetragonal for BaTiO3 obtained by Pechini process and tetragonal for BaTiO3 obtained by mechanically assisted synthesis