Search

Three different methods were used to obtain Bi5Ti3FeO15 ceramics, i.e. solid-state sintering, mechanical activation (MA) with subsequent thermal treatment, and electrical discharge assisted mechanical milling (EDAMM). The structure and magnetic properties of produced Bi5Ti3FeO15 samples were characterized using X-ray diffraction and Mössbauer spectroscopy. The purest Bi5Ti3FeO15 ceramics was obtained by standard solid-state sintering method. Mechanical milling methods are attractive because the Bi5Ti3FeO15 compound may be formed at lower temperature or without subsequent thermal treatment. In the case of EDAMM process also the time of processing is significantly shorter in comparison with solid-state sintering method. As revealed by Mössbauer spectroscopy, at room temperature the Bi5Ti3FeO15 ceramics produced by various methods is in paramagnetic state.

In the present work the influence of rare earth elements concentration (0-10at-%) on BiFeO3:RE (RE=Gd3+, Dy3+, Nd3+) ceramics were studied. All ceramic powders were synthesized by conventional ceramic method using high purity raw materials (>99,9%), and subsequently sintered by free sintering and cold pressing method. To analyze the powders and ceramics more the XRD, EDS, SEM, and DTA were performed.

In this work, BiFeO3 powders were synthesized by a sol–gel method. The influence of annealing temperature on the structure and magnetic properties of the samples has been discussed. X-ray diffraction studies showed that the purest phase was formed in the temperature range of 400 °C to 550 °C and the samples annealed at a temperature below 550 °C were of nanocrystalline character. Mössbauer spectroscopy and magnetization measurements were used as complementary methods to investigate the magnetic state of the samples. In particular, the appearance of weak ferromagnetic properties, significant growth of magnetization, and spin-glass-like behavior were observed along with the drop of average grain size. Mössbauer spectra were fitted by the model assuming cycloidal modulation of spins arrangement and properties of the spin cycloid were determined and analyzed. Most importantly, it was proved that the spin cycloid does not disappear even in the case of the samples with a particle size well below the cycloid modulation period λ = 62 nm. Furthermore, the cycloid becomes more anharmonic as the grain size decreases. The possible origination of weak ferromagnetism of the nanocrystalline samples has also been discussed. [ABSTRACT FROM AUTHOR]

Aurivillius Bi5Ti3FeO15 (BTF) and Bi5-xNdxTi3FeO15 (BNTF) ceramics were successfully synthesized by a simple solid state reaction method. Ceramics were prepared from simple oxide powders Bi2O3, TiO2, Nd2O3 and Fe2O3. The microstructure, structure, chemical composition and dielectric properties of the obtained materials were examined. Dielectric properties were investigated in a wide range of temperatures (T = 25°C-550°C) and frequencies (20Hz-1MHz). [ABSTRACT FROM AUTHOR]

Aurivillius Bi5-xHoxTi3FeO15 (BHTFO) multiferroic ceramics with different holmium doping contents were synthesized by conventional solid state reaction. The effect of holmium doping on the microstructure, structural and dielectric behaviors of BHTFO ceramics were investigated in details. Microstructure and crystalline structure studies of ceramics were carried out at room temperature while dielectric properties were investigated in a wide range of temperature (T = 25°C-550°C) and frequency (20Hz-1MHz). [ABSTRACT FROM AUTHOR]

The aim of these studies was to obtain single phase cubic modification of Li7La3Zr2O12 by mechanical milling and annealing of La(OH)3, Li2CO3 and ZrO2 powder mixture. Fritsch P5 planetary ball mill, Rigaku MiniFlex II X-ray diffractometer, Setaram TG-DSC 1500 analyser and FEI Titan 80-300 transmission electron microscope were used for sample preparation and investigations. The applied milling and annealing parameters allowed to obtain the significant contribution of c-Li7La3Zr2O12 in the sample structure, reaching 90%. Thermal measurements revealed more complex reactions requiring further studies. [ABSTRACT FROM AUTHOR]

The aim of this research was to fabricate and study the properties of Bi1-x DyxFeO3 (for x = 0, 0.05, 0.07, 0.1) ceramics materials. Simple oxide powders Bi2O3, Dy2O3 and Fe2O3 were used to fabricate Bi1-xDyxFeO3 ceramics by mixed oxide method followed by free sintering. The study presents changes in microstructure and crystal structure as well as in dielectric properties and magnetic properties caused by modification of BiFeO3 with dysprosium dopant. [ABSTRACT FROM AUTHOR]

Delafossite CuFeO2 belongs to multiferroic class of materials. In this work, copper ferrite was prepared by mechanical activation with subsequent thermal treatment. X-ray diffraction and Mössbauer spectroscopy were used as complementary methods to study the structure and hyperfine interactions of the material. As proved by X-ray diffraction, CuFeO2 compound was obtained with relatively low amount of secondary phases like CuO and CuFe2O4. The Mössbauer spectroscopy revealed paramagnetic character of the compound at room temperature. The purest delafossite CuFeO2 was obtained by mechanical activation of pre-milled precursors and sintering at 1173 K. The temperature of thermal treatment is lower by 100 K as compared to the traditional solid-state synthesis. [ABSTRACT FROM AUTHOR]

Delafossite CuFeO2 belongs to multiferroic class of materials. In this work, copper ferrite was prepared by mechanical activation with subsequent thermal treatment. X-ray diffraction and Mössbauer spectroscopy were used as complementary methods to study the structure and hyperfine interactions of the material. As proved by X-ray diffraction, CuFeO2 compound was obtained with relatively low amount of secondary phases like CuO and CuFe2O4. The Mössbauer spectroscopy revealed paramagnetic character of the compound at room temperature. The purest delafossite CuFeO2 was obtained by mechanical activation of pre-milled precursors and sintering at 1173 K. The temperature of thermal treatment is lower by 100 K as compared to the traditional solid-state synthesis. [ABSTRACT FROM AUTHOR]

Three different methods were used to obtain Bi5Ti3FeO15 ceramics, i.e. solid-state sintering, mechanical activation (MA) with subsequent thermal treatment, and electrical discharge assisted mechanical milling (EDAMM). The structure and magnetic properties of produced Bi5Ti3FeO15 samples were characterized using X-ray diffraction and Mössbauer spectroscopy. The purest Bi5Ti3FeO15 ceramics was obtained by standard solid-state sintering method. Mechanical milling methods are attractive because the Bi5Ti3FeO15 compound may be formed at lower temperature or without subsequent thermal treatment. In the case of EDAMM process also the time of processing is significantly shorter in comparison with solid-state sintering method. As revealed by Mössbauer spectroscopy, at room temperature the Bi5Ti3FeO15 ceramics produced by various methods is in paramagnetic state. [ABSTRACT FROM AUTHOR]

Abstract: The structure, hyperfine interactions and magnetic properties of the series of multiferroic Bi m+1Ti3Fe m−3O3m+3 Aurivillius compounds with m=4–8 were studied using X-ray diffraction, 57Fe Mössbauer spectroscopy and vibrating sample magnetometry. Samples were prepared by the conventional solid-state sintering method. Bulk magnetic measurements showed that for m=4 the compound is paramagnetic down to 2K while in the compound with m=5 the antiferromagnetic type transition was observed at 11K. In the case of compounds with m=6–8 much more complex magnetic behavior was found. For these compounds a gradual spin freezing and antiferromagnetic spin glass-like ordering were observed on decreasing temperature. The temperature of spin glass freezing was determined as 260, 280 and 350K for m=6, 7 and 8, respectively. Room-temperature Mössbauer spectra of all the compounds studied confirm their paramagnetic state. However, liquid nitrogen and liquid helium temperature measurements reveal magnetic ordering with a residual paramagnetic phase contribution for the compounds with m=5–8. [Copyright &y& Elsevier]

Co40Fe50Ni10 and Co50Fe45Ni5 ternary alloys were prepared by mechanical alloying method. To check the stability of their structure thermal treatment was applied subsequently. As X-ray diffraction studies proved the final products of milling were the solid solutions with bcc lattice and the average grain sizes ranged of tens of nanometers. After heating of the Co50Fe45Ni5 alloy up to 993 K the mixture of two solid solutions with bcc and fcc lattices was formed. In other cases thermal treatment did not change the type of the crystalline lattice. Mössbauer spectroscopy revealed hyperfine magnetic field distributions which reflected the different possible atomic surroundings of 57Fe isotopes. Results of the macroscopic magnetic measurements proved that both investigated alloys had relatively good soft magnetic properties. [ABSTRACT FROM AUTHOR]