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 °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

One hundred millipede species in Serbia (Arthropoda: Myriapoda: Diplopoda)

The millipede fauna of Serbia consists of 100 species, 44 genera, 16 families and 7 orders. The most abundant are families Julidae (41 species or 41%) and Polydesmidae (22 species or 22%). Of the total number, 27 species (27%) are endemic to Serbia, while 18 (18%) are endemic to the Balkan Peninsula. All registered species can be related to 15 zoogeographical categories. Glomeris klugii Brandt, 1833 (Glomerida: Glomeridae), Cibiniulus phlepsii (Verhoeff, 1897) (Julida: Blaniulidae), Brachyiulus bagnalli (Brolemann, 1924), Megaphyllum carniolense (Verhoeff, 1897), Typhloiulus incurvatus Verhoeff, 1899, Xestoiulus luteus (Attems, 1951) (all Julida: Julidae), and Polydesmus renschi Schubart, 1934 (Polydesmida: Polydesmidae) represent new records for the diplopod fauna of Serbia. [Projekat Ministarstva nauke Republike Srbije, br. 173038

Synthesis of BaTiO3 from a mechanically activated BaCO3-TiO2 system

In this article the solid state reaction of BaTiO3 formation from a mechanically activated BaCO3-TiO2 system has been investigated. An equimolar mixture of BaCO3 and TiO2 powders was activated in a planetary ball mill in a continual regime for 0, 30 and 90 min, pressed and thermally treated up to 1200°C. The effect of the milling and firing regime on the phase formation was investigated by the X-ray diffraction (XRD) method and differential thermal analysis (DTA). Deconvolution of the experimental DTA curve corresponding to the BaTiO3 synthesis process has been performed. The influence of the activation time on the change of characteristic temperature for each elementary step in the complete solid-state reaction of BaTiO3 formation, was analyzed. These results were correlated with the ones obtained by SEM characterization and by XRD analysis.U ovome radu je analiziran uticaj mehaničke aktivacije sistema BaCO3- TiO2 na formiranje BaTiO3. Ekvimolarne smeše praha BaCO3 i TiO2 su aktivirane u planetarnom mlinu u kontinualnom režimu tokom 0, 30 i 90 min. Uzorci su zatim presovani i termički tretirani do 1200oC. Efekat mlevenja i zagrevanja na promene faza je analiziran primenom rendgenske fazne analize i diferencijalne termijske analize. Izvršena je dekonvolucija eksperimentalno dobijene DTA krive koja odgovara procesu sinteze BaTiO3, kao i analiza uticaja vremena aktivacije na promene karakteristične temperature za svaki pojedinačni elementarni proces tokom sinteze barijum titanata. Ovi rezultati su korelisani sa rezultatima dobijenim SEM i XRD analizom

A new cave diplopod of the genus Brachydesmus heller, 1858 from southwest Serbia (Diplopoda: Polydesmida: Polydesmidae)

A new cave polydesmid, Brachydesmus sjenicae n. sp. is described from Ledena Pećina Cave, in southwest Serbia. The new taxon belongs to the vermosanus-group of species. Relationships with congeners are briefly discussed. The distribution map and key is given for all currently known taxa belonging to this group of species. [Projekat Ministarstva nauke Republike Srbije, br. 173038

History and challenges of barium titanate: Part I

Barium titanate is the first ferroelectric ceramics and a good candidate for a variety of applications due to its excellent dielectric, ferroelectric and piezoelectric properties. Barium titanate is a member of a large family of compounds with the general formula ABO3 called perovskites. Barium titanate can be prepared using different methods. The synthesis method depends on the desired characteristics for the end application. The used method has a significant influence on the structure and properties of barium titanate materials. In this review paper, Part I contains a study of the BaTiO3 structure and frequently used synthesis methods

Structural and ferroelectrical properties of bismuth titanate ceramic powders prepared by mechanically assisted synthesis

Nanosized bismuth titanate, Bi4Ti3O12, was prepared via a high-energy ball milling process through mechanically assisted synthesis directly from the oxide mixture of Bi2O3 and TiO2. The Bi4Ti3O12 phase started to form after 1 h of milling. With increasing the milling time from 3 to 12 h, the particle size of formed Bi4Ti3O12 did not reduce significantly. The grain size was less than 16 nm and showed a strong tendency to agglomeration. The nucleation and phase formation of Bi4Ti3O12, crystal structure, microstructure, powder grain size and specific surface area were followed by XRD, Rietveld refinement analysis, SEM and the BET specific surface area measurements. Raman spectroscopy was used to explain the structural properties of Bi4Ti3O12 powder, prepared by mechanically assisted synthesis. Reduction in grain size with the increase of milling time was also noted (change in the position and relative intensity), which indicated changes in the structure, caused by nanodimension grains. The sample milled for 12 h and subsequently sintered at 1000°C for 24 h exhibited a hysteresis loop, confirming that the synthesized material possesses ferroelectric properties.

Mechanochemical activation assisted synthesis of bismuth Layered-Perovskite Bi4Ti4O12

A powder mixture of Bi2O3 and TiO2, both monoclinic, was mechanochemically treated in a planetary ball mill in air atmosphere for different time, using zirconium balls as the milling medium. Mechanochemical reaction leads to the gradual formation of an amorphous phase. After 1 h of milling the starting oxides were transformed fully a nanocrystalline Bi4Ti4O12 phase. With increasing the milling time from 3 to 12h, the particle size of formed Bi4Ti3O12 did not reduced significantly. That was confirmed by IR and TEM analysis. The electron diffraction pattern indicates that Bi4Ti3O12 crystalline powder is embedded in an amorphous phase of bismuth titanate. Phase composition and atom ratio in BIT ceramics were determined by X-ray diffraction and EDS analysis. After milling for various times the powders were compacted by pressing and isothermal sintering. The dielectric permittivity of the sintered samples significantly depends on the milling time. Sample milled for 12 h and subsequently sintered at 1000°C for 24 h exhibit a hysteresis loop, confirming that the synthesized material possesses ferroelectric properties

Screen printed barium titanate thick films prepared from mechanically activated powders

Barium titanate thick films were prepared from mechanically activated powders based on BaCO3 and TiO2. The thick films were screen-printed on alumina substrates electroded with Ag/Pd. The BT films were sintered at 850°C for 1 hour. The thickness was 30-75 μm depending of number of layers. The microstructure of thick films and the compatibility between BT layers and substrate was investigated by SEM. The dielectric properties were measured and the results were reported

Screen printed barium titanate thick films prepared from mechanically activated powders

Barium titanate thick films were prepared from mechanically activated powders based on BaCO3 and TiO2. The thick films were screen-printed on alumina substrates electroded with Ag/Pd. The BT films were sintered at 850°C for 1 hour. The thickness was 30-75 μm depending of number of layers. The microstructure of thick films and the compatibility between BT layers and substrate was investigated by SEM. The dielectric properties were measured and the results were reported