Analysis of isothermal sintering of zinc-titanate doped with MgO

The aim of this work was analysis of isothermal sintering of zinc titanate ceramics doped with MgO obtained by mechanical activation. Mixtures of ZnO, TiO2 and MgO (0, 1.25 and 2.5%) were mechanically activated 15 minutes in a planetary ball mill. The powders obtained were pressed under different pressures and the results were fitted with a phenomenological compacting equation. Isothermal sintering was performed in air for 120 minutes at four different temperatures. Structural characterization of ZnO-TiO2-MgO system after milling was performed at room temperature using XRPD measurements. DTA measurements showed different activation energies for pure and doped ZnO-TiO2 systems. Thus addition of MgO stabilizes the crystal structure of zinc titanate

Synthesis And Structure Of LiMn2-XZnxO4 Through Ultrasonic Spray Pyrolysis

Poster presented at the VIII Conference on Fundamental and. Applied Aspects of Physical Chemistry 2006, Beograd, 26-29. septembar 2006

Synthesis and structure of LiMn2-xZnxO4 through ultrasonic spray pyrolysis

Ultrasonic spray pyrolysis method was used for the synthesis of quaternary spinel oxide LiMn2-xZnxO4 (x ≈ 0.08) powder, without additional annealing. Aqueous solutions of metal nitrates were atomized at a frequency of 1.7 MHz by the ultrasonic nebulizer. Aerosol was introduced in the horizontal electric furnace at the temperature of 1073 K. The crystal structure of the as-prepared powder was revealed by Xray powder diffraction and identified as a single spinel phase with Fd3m space group. Particle morphology was determined by scanning electron microscopy (SEM).Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Phonon Investigations in YVO4: Eu3+ Nanopowders

In this work two methods of preparation of yttrium orthovanadate nanopowders were presented: Solid State Reaction (top – down approach) and Solution Combustion Synthesis (bottom – up approach). For starting structural characterization, X – Ray Powder Diffraction (XPRD) and Field Emission Scanning Electron Microscopy (FESEM) were used. We report the change in reflection spectra in europium doped YVO4 nanopowders with comparison to its bulk analog. In UV – Vis reflection spectra we consider the change in values of band gap in these structures, after resizing it from bulk to nanomaterial. In Far – Infrared (FIR) reflection spectra, we registered the existence of Surface Optical Phonon (SOP) and different multi – phonon processes which alter the reflection spectra of bulk YVO4 . The influence of Eu ions is reflected through multi – phonon processes that occur and are connected with energy transfer from YVO4 lattice to Eu ions. All IR spectra were modeled using classical oscillator model with Drude part added which takes into account the free carrier contribution. Since our samples are distinctively inhomogeneous materials, we use Effective Medium theory in Maxwell Garnett approximation to model its effective dieletric function.IX Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 20-21, 2021; Belgrad

The Influence of Compaction Pressure on the Density and Electrical Properties of Cordierite-based Ceramics

Due to its characteristics, cordierite, 2MgO center dot 2Al(2)O(3)center dot 5SiO(2), is a high-temperature ceramic material of a great scientific interest. Mechanical activation of the starting mixtures containing 5.00 mass% TiO2 was performed in a high-energy ball mill for 10 minutes. The compaction pressure varied from 0.5 to 6tcm(-2) (49-588 MPa). The sintering process was performed at 1350 degrees C for four hours in the air atmosphere. The phase composition of the activated and sintered samples was analyzed using X-ray diffraction. Scanning electron microscopy was used to analyze the microstructure of both compacted and sintered samples. The authors have investigated the influence of compaction pressure on the sintered samples and their electrical properties

Influence of mechanical activation on microstructure and crystal structure of sintered MgO-TiO2 system

Mixtures of MgO-TiO2 were mechanically activated using high-energy planetary ball mill during 5, 10, 20, 40, 80 and 120 minutes. Sintering process was preformed in air at 1100°-1400°C for 2h. The decrease in powder's particle size was noticed as the time of mechanical activation increased and confirmed by particle size analyzer. XRD analyses were performed in order to acquire the information about phase composition. Different ratio mixtures of MgTiO3 and Mg2TiO4 are present within all sintered samples. The effect of tribophysical activation on microstructure was investigated by scanning electron microscopy. The differential thermal gravimetric analysis has been performed in order to investigate thermal behaviour of the mixtures.Smeše MgO-TiO2 su mehanički aktivirane u visoko-energetskom planetarnom mlinu tokom 5, 10, 20, 40, 80 i 120 minuta. Fazni sastav je određen rendgenskom difrakcijom. Sa porastom vremena mlevenja, primećeno je smanjenje veličine čestica praha. Takođe, ispitan je i efekat tribofizičke aktivacije na mikrostrukturu praha metodom skenirajuće elektronske mikroskopije. Radi ispitivanja termičkih svojstava praha, urađena je diferencijalna termijska analiza. Proces sinterovanja izveden je u vazduhu u temperaturnom opsegu od 1100°-1400°C tokom 2 sata. U svim sinterovanim uzorcima uočeno je prisustvo dve faze MgTiO3 i Mg2TiO4 ali njihov međusobni odnos koncentracija varira u odnosu na temperaturu sinterovanja

Structural and Electrical Properties of Barium-Zinc-Titanate Ceramics Sintered at 1300°C

Poster presented at the 12th Annual Conference of the Materials Research Society of Serbia - YUCOMAT 2010, Herceg Novi, Montenegro, September 6–10, 2010

Synthesis, structural and magnetic properties of Y1-xYbxF3 solid solution

Many works devoted to obtaining nanodispersed BaTiO3 powder modified with different dopants for suitable properties providing. In particular, recently considerable attention has been given to obtaining modified nanopowders BaTiO3 possessing relaxor behavior order to ensure reliable work of dielectrics. Generally, Ca,Zr,Mn, ,Pb and rare earth elements such as Nb,Y adds order to provide stress, inhibit grain growth and provide Pinching effect, and hence to increase dielectrics relaxor behavior. However, there is still an issue associated with obtaining satisfactory stoichiometry of the obtained powder. From this viewpoint Ca,Zr-doped BaTiO3 were prepared with co-precipitation method via multiligand complexes formation and influence of the precursor type on Ca,Zr-doped BaTiO3 stoichiometry were investigated. Their stoichiometry, crystal structure was examined in order to determine preferential solubility site of Ca,Zr ions in perovskite structure. Stoichiometry Ca,Zr-modified BaTiO3 will be evaluated considering different precursor type. X-ray, IR spectroscopy and X-ray fluorescence analysis were carried out to obtain the knowledge on the occupation site in the Ba1-xСaxTi1-yZryO3 perovskite structure. These results proved influence complex formation on Ca,Zr-modified BaTiO3 stoichiometry

CaCu3Ti4-xRuxO12: Crystal structure, electrical and magnetic properties

The CaCu3Ti4O12 belongs to the large ACu3B4O12 family of materials. Crystallographic A site is most often occupied by alkaline-earth metals or lanthanides, while B site is occupied by transition metals. The type of cations that build up the structure strongly affects the properties of these. The CaCu3Ti4O12 has been extensively studied due to its high dielectric permittivity stable over a wide temperature and frequency range (up to 105, for 100-600 K and 102–105 Hz). Because of such characteristics, it has promising application in microelectronics. However, it has been shown that differences in the crystal structure and electrical properties of dielectric ceramics and metallic electrodes, may cause an energy barrier and occurrence of stress on the ceramic-electrode contact which reduces dielectric permittivity. Such stress can be prevented by using dielectric and electrode materials with as much as possible similar crystal structure, especially unit cell parameters. This investigation dealt with detailed structural (XRPD, HRTEM, SAED), dielectric and magnetic study of CaCu3Ti4-xRuxO12 (CCTRO, x = 0, 1 and 4) materials. The results of structural refinement show that in cubic symmetry with space group Im3 , both titanium and ruthenium ions occupied crystallographic B site. Moreover, the variation in stoichiometry slightly affects the value of the unit cell parameters but changes electrical properties of studied material. Thus, substitution of even one atom of Ru in CaCu3Ti4-xRuxO12 unit cell is enough to change material properties from dielectric to conductor solving the problem of stress appearance on the contact layer of dielectric/electrode in capacitors

Colloidal-chemistry based synthesis of quantized CuInS2/Se2 nanoparticles

Ternary chalcogenide nanoparticles, CuInS2 and CuInSe2, were synthesized in high- temperature boiling organic non-polar solvent. The X-ray diffraction analysis revealed that both materials have tetragonal (chalcopyrite) crystal structure. Morphology of the obtained materials was revealed by using transmission electron microscopy. Agglomerated spherical CuInS2 nanoparticles with broad size distribution in the range from 2 to 20 nm were obtained. In the case of CuInSe2, isolated particles with spherical or prismatic shape in the size range from 10 to 25 nm were obtained, as well as agglomerates consisting of much smaller particles with diameter of about 2-5 nm. The particles with the smallest diameters of both materials exhibit quantum size effect