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Structural, electrical and magnetic properties of nickel manganite ceramics obtained by sintering fine powders prepared by a complex polymerization method are given in this work. The phase composition of the synthesized material was examined by x-ray powder diffraction (XRPD). Field-emission scanning electron microscopy (FE-SEM) was used to analyze the obtained powder morphology. Scanning electron microscopy (SEM) was used to analyze the microstructure of sintered ceramics. The activation energy of conduction E-a and the coefficient of temperature sensitivity B-25/100 were calculated from direct current (DC) resistivity measurements. The magnetization dependence of temperature M(T) and alternating current (AC) susceptibility data obtained from SQUID measurements clearly demonstrate that quadruple magnetic phase transitions can be readily detected at T-M1 similar to 115 K, T-M2 similar to 105 K, T-M3 similar to 38 K and T-M4 similar to 7 K. These findings suggest a novel magnetic transition for nickel manganite at low temperature T-M4.

A powder mixture of Bi2O3 and Fe2O3 was mechanically treated in a planetary ball mill in an air from 30 to 720 minutes. It was shown that the mechanochemical formation of BiFeO3 (BFO) phase was initiated after 60 min and its amount increased gradually with increasing milling time. A detailed XRPD structural analysis is realized by Rietveld's structure refinement method. The resulting lattice parameters, relative phase abundances, crystallite sizes and crystal lattice microstrains were determined as a function of milling time. Microstructural analysis showed a little difference in morphology of obtained powders. The primary particles, irregular in shape and smaller than 400 nm are observed clearly, although they have assembled together to form agglomerates with varying size and morphology. Dense BFO ceramics were prepared by conventional solid-state reaction at the temperature of 810oC for 1h followed immediately by quenching process.

We have studied the formation of BiMnO3 (BMO) nanocrystalline perovskite powder produced by high-energy milling of the constituent oxides. The crystal structure and the amount of crystalline and amorphous phases in the powder as a function of the milling time were determined with XRPD using Rietveld refinement. BMO perovskite formed directly from highly activated nano-sized constituent oxides after 240 min of milling and subsequently grew during prolonged milling. The morphology, structure, and chemical composition of the powder were investigated by SEM and TEM. A clear ferromagnetic transition was observed at T (C) similar to 66 K for a sample milled for 240 min and increased with milling time. The magnetic hysteresis behavior is similar to that of a soft ferromagnet. The magnetic properties of the obtained BMO powders were found to change as a function of milling time in a manner consistent with variations in the nanocomposite microstructure.

Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese and nickel oxide was additionally mechanically activated in a high energy planetary ball mill for 5-60 min in order to obtain a pure NiMn2O4 phase. The as-prepared powders were uniaxially pressed into disc shape pellets and then sintered for 60 min at 1200 degrees C. Changes in the particle morphology induced by mechanical activation were monitored using scanning electron microscopy, while changes in powder structural characteristics were followed using X-ray powder diffraction. The ac impedance spectroscopy was performed on sintered nickel manganite samples at 25 degrees C, 50 degrees C and 80 degrees C. It was shown that mechanical activation intensifies transport processes causing a decrease in the average crystallites size, while longer activation times can lead to the formation of aggregates, defects and increase of lattice microstrains. The observed changes in microstructures were correlated with measured electrical properties in order to define optimal processing conditions.

Multiferroic bismuth manganite (BiMnO3) is known as a material that exhibits both ferromagnetic and ferroelectric properties making it interesting for various technological applications. Unfortunately, preparation of BiMnO3 is not possible by a conventional solid-state reaction and it can form only from mixture of oxides at high pressures (>40 kbar). In this work single-phased BiMnO3 was prepared for the first time by mechanochemical synthesis in a planetary ball mill. A mixture of Bi2O3 and Mn2O3 was intensively milled in air atmosphere, using stainless steel vials and balls. According to analysis of XPRD results BiMnO3 obtained after milling for 240 min has a tetragonal structure with lattice parameters a = 3.9230 angstrom, c = 3.920 angstrom and a crystallite size of 16.8 nm. The cumulative energy introduced into the system during milling for 240 min was 401 kJ/g. It was found that the obtained powders were agglomerated. Corresponding agglomeration factors were calculated from the results of BET and particle size distribution analysis.

Single-phase zinc-stannate thin films of different thickness values were prepared by radio frequency magnetron sputtering on a silica substrate. Rietveld analysis of X-ray diffraction data confirmed that the films had an inverse spinel structure, with a cation inversion parameter of 0.8. Room temperature far and mid infrared reflectivity spectra were measured in the range 50-4000 cm(-1). The reflectivity diagrams were analyzed using the four-parameter model of coupled oscillators for optical phonons with a standard multi-layer technique taking into account the thin-film layer and the substrate. The optical parameters were determined for seven oscillators belonging to the spinel structure. Their origin was discussed in relation to non-stoichiometry of the thin film and cation disorder in the crystal lattice. Bom effective charges were calculated from the transversal/ longitudinal splitting.

The common nitrates precursor solution leading to the Y3Al5O12:Ce3+ (YAG:Ce) composition with 2 at.% of cerium, is ultrasonically atomised and introduced into the tubular flow reactor at 320 degrees C. Having in mind that extremely high heating rates and short residence time are associated with spray pyrolysis, the low temperature regime is used for aerosol decomposition for the production of segregation-free precursor powder that is additionally heated at 900 and 1000 degrees C (2-6h) for the purpose to determine the phase evolution. Formation of uniform and submicron-sized spherical particles with nano-clustered inner structure is proved by different analysing techniques (X-ray powder diffraction, scanning electron microscopy and energy dispersive spectroscopy). The effect of processing parameters and post-annealing treatment is discussed from the viewpoint of the targeted garnet phase formation.

An equimolar mixtures of starting ZnO and Cr2O3 powders were mechanically activated by grinding using a planetary ball mill for various periods of time (40-320min). Formation of nanocrystalline ZnCr2O4 as normal spine] structure at room temperature is detected in all samples-after ball-milling. A detailed XRD structural analysis (the relative phase abundances of different phases, lattice parameter changes, site occupancy, the average primary crystallite sizes, crystal lattice microstrains) is realized by the pattern decomposition technique, performed in accordance with the procedure based on Rietveld software KOALARIET-XFIT. Due to the importance of cation distribution on the chemical and physical properties of spinels, a study of site occupation factors of ZnCr2O4 spinels has been undertaken. The calculation based on the atomistic methods for the description of the perfect and defect spinel ZnCr2O4 crystal lattice is applied and the presence of the individual structural defects is determined.

Razvoj novih materijala, kao i nastojanja za iskorišćenjem njihovih tehnološki atraktivnih karakteristika doveli su do intenzivnije sinteze novih ultrafinih struktura i nanofaznih prahova. Istraživanja obuhvaćena radom fokusirana su na dirigovanu sintezu nanostrukturnih oksidnih prahova iz sistema koje odlikuje izrazita jonska (ZnCr2O4) i elektronska provodnost(Bi1.8Pb0.2Sr2Ca2Cu3Ox) primenom metode reakcionog raspršivanja. Akcenat je stavljen na nastanak faza koje su potencijalni nosioci svojstava značajnih za tehničku primenu materijala. Primenjena strategija rezultat je razvoja metode sa stanovišta definisanja odnosa u trijadi sinteza-struktura-svojstvo i izvodjenja procesa kontrolisane sinteze. Proces sinteze ZnCr2O4 praha izveden je u uslovima ultrazvučnog reakcionog raspršivanja rastvora nitrata koncentracije 0.03mol/dm3 pri unapred definisanim parametrima procesa i za različito vreme zadržavanja kapi/čestice na Tmax uz dodatan boravak u reakcionim zonama sa nižom temperaturom. Čestice nastaju procesom zapreminskom precipitacije, nukleacije, rasta kristala i obrazovanja primarnih nanočestica koje nisu u slobodnom stanju vec izgradjuju agregate sferičnog oblika i srednje veličine 470nm. Za prah iz filtra karakterističan je nastanak čestica ZnCr2O4 na čijoj se površini jasno uočavaju primarne čestice veličine nekoliko desetina nanometra. Strukturna analiza ovog praha pokazuje prisustvo primarnih kristalita veličine 44nm, i najveću utvrdjenu vrednost mikronaprezanja, 0.638%. Produženje vremena boravka čestica u reakcionoj zoni dovodi do promene morfologije prahova, pri čemu je za čestice praha zone I karakteristično nastajanja punih čestica, glatke površine i homogenog sastava. Veličina primarnih kristalita odredjena na bazi strukturne difraktometrijske analize iznosi 33nm. Na bazi faktora okupiranosti katjonskih položaja u jediničnoj ćeliji spinela utvrdjeni odnos katjona Zn i Cr blizak je zadatoj vrednosti (0.5) i iznosi: 0.496 (prah zone I), 0.481 (prah zone I, Development of advanced materials, together with the efforts invested in the optimization of their current properties result today in the opening of a new field: design of ultra-fine structure materials. Nanostructured materials with new and improved properties could be prepared through different techniques. Investigations presented here are focused on conducted synthesis of nanostructured oxide powders in ZnCr2O4 and Bi1.8Pb0.2Sr2Ca2Cu3Ox systems using the spray pyrolysis method. The main emphasis is on controlled evolution of specific phases characterized with properties suitable for potential technical application. The strategy used is the result of methodology development from the viewpoint of establishing synthesis-structure-properties relations. Because of that, investigation of phase thermal stability, particle morphology - shape, size and agglomeration, crystal structure - grain boundary and defects concentration, homogeneity of chemical composition are of special interest. As a result of ZnCr2O4 powder conduction synthesis using spray pyrolysis of nitrate salts, spherical particles with uniform size around 470 nm are obtained. Synthesized dense particles are uniform in shape and posses small differences in crystallinity and stoichiometry. Effect of droplet/particle residence time on final powder morphology is established through investigation of precursor decomposition, nucleation and growth of primary crystallites in nanoporous precipitated particles. It was shown that increase of the residence time indicates growth of nanocrystallites with mean sizes around 40nm leading to dense particle evolution. Also, formation of a spinel phase with high homogeneity and uniformity of chemical composition in all produced samples are characterized with the cation ratio of Zn/Cr=0.68. Constant mismatching in stoichiometry from the assigned value, as well as additional changes in particle morphology after their thermal treatment at 1000 °C (2h) is the consequence of ZnO d

Mixtures of starting ZnO and Cr2O3 powders in equimolar quantities were mechanically activated by grinding using a high energy vibro-mill for 0, 40 and 80 minutes. Qualitative X-ray diffraction analysis made after sintering at 900degreesC for 240 min showed the presence of a well-crystallized spinel-type phase, ZnCr2O4, in all examined samples. A detailed structural analysis of lattice parameters, average primary crystallite sizes, and crystal lattice microstrains was made by the pattern decomposition technique, performed in accordance with the procedure based on the KOALARIET-XFIT program. Due to importance of cation distributions for the chemical and physical properties of spinels, a study of site occupation factors of ZnCr2O4 spinels, i.e. changes in the stoichiometry, was conducted. Calculations based on atomistic methods for the simulation and description of perfect and defect spinel ZnCr2O4 crystal lattices were made, and the presence of individual structural defects was determined.

Nanocomposite powders in the system (La1-xSx)(a)MnO3-YSZ((1-y)) [LSM-YSZ], as an attractive cathode material for high operating solid oxide fuel cell (SOFC), were obtained through ultrasonic spray pyrolysis (1.7 MHz) method. The principle of the synthesis is based on a single-step high temperature aerosol decomposition of atomized precursor solutions composed from yttria stabilized ZrO2 sol (average particle size similar to 60 nm) and corresponding aqueous nitrate and hydrogen peroxide solutions of La, Sr and Mn. Two starting systems were examined: (a) (La0.76Sr0.24)(0.93)MnO3 with 0% YSZ, and (b) (La0.77Sr0.23)(0.92)MnO3-YSZ(0.81) with corresponding molar ratio LSM/YSZ = 48:52. X-ray diffraction analysis of as-prepared powders showed the presence of a lanthanum magnesium oxide and yttrium zirconium oxide. Compositional homogeneity and particle morphology were determined by SEM analysis. LSM-YSZ obtained particles are spherical in shape, submicron in size and composed of primary subgrains. TEM analysis of ultra-cross section revealed dense-packed nanosized grains, several tens of nanometers in diameter. After powders calcination TEM observations confirmed dense particle structure composed of primary grains, with a mean diameter of around 100 nm. The structural changes expressed through the crystallite growth were analyzed by nonisothermal differential scanning calorimetry (DSC).

The nature of exothermal and irreversible structural changes observed during linear heating of nanocrystalline ZnO powders was investigated using differential scanning calorimetry, X ray, SEM and TEM analysis. Nanocrystalline ZnO powders were obtained by ultrasonic spray pyrolysis of 0.8 mol/dm(3) zinc nitrate solution and subsequent decomposition of 2.7 mum sized droplets in the temperature range up to 600 degreesC, F-air = 1.2 dm(3)/min. Produced particles are characterized by uniform and submicronic size, BET = 4.94 m(2)/g, high phase purity and granular or circular "open" surface as the consequence of primary crystallites presence with average size of d = 20 nm. The observed quasi nucleation-growth process during heating of this powder was discussed in the terms of primary crystallites structural changes.

Polycrystalline tin oxide thin films were prepared from ethanol solution Of SnCl2.H2O (concentrations: 0.05, 0.1, 0.2 and 0.4 mol/dm(3)) at different substrate temperatures ranging from 300 to 450 degreesC. The kinetic deposition processes were studied in terms of various process parameters. The crystal phases, crystalline structure, grain size and surface morphology are revealed in accordance to X-ray diffractometry and scanning electron microscopy (SEM). Texture coefficients (TCs) for (110), (2 0 0), (2 11) and (3 0 1) reflections of the tetragonal SnO2 were calculated. Structural characteristics of deposited films with respect to varying precursor chemistry and substrate temperature are presented and discussed.

Among many aerosol routes, the Pyrosol process, due to its simplicity, low cost and quality of obtained films, represents a promising technique for the synthesis of thin films. The pyrosol process is based on the transport and pyrolysis of an aerosol of processor solution, generated in an ultrasonic atomizer, on a heated substrate. The theoretical principles of the pyrosol process are presented in this paper, as well as the influence of some synthesis parameters on the deposition of SnO2 thin films.

Ultrasonic spray pyrolysis (1.7 MHz) has been applied for the generation of zinc chromium oxide submicronic (470 nm) particles from the corresponding metal nitrate solution. Heterogeneous gas-liquid/solid chemical reactions occurred in dispersed systems (aerosols) at 1173 K with the residence time ranging from 3 to 6 s. Such a synthesis method enables a high surface reaction and stoichiometric retention at the droplet scale that is of special importance when functional materials with sensing properties are considered. Consequently, homogeneous distributions of the constituting elements and zinc to chromium atomic ratio of about 0.7 are proved by EMAX analysis. The particle morphology, revealed mostly as a composite structure, comprised of primary crystallites smaller than 70 nm. The particle crystalline structure, phase content and decomposition behavior were analyzed in accordance with various methods of analysis (X-ray powder diffraction (XRD). differential scanning calorimetry (DSC). differential thermal analysis (DTA), scanning electron microscopy with X-ray microanalyser (SEM-EMAX)) and discussed in terms of precursor chemistry and process parameters.