Defect induced weak ferroelectricity and magnetism in cubic off-stoichiometric nano bismuth iron garnet: effect of milling duration (original) (raw)
Related papers
Advanced Materials Research, 2014
Multiferroic bismuth ferrite, BiFeO 3 , was synthesized via conventional solid-state reaction method using Bi 2 O 3 , Fe 2 O 3 as starting materials. Effects of Bi 2 O 3 /Fe 2 O 3 molar ratio and calcination temperature on the phase composition, morphology and magnetic properties of produced powders were systematically studied using XRD, FESEM/EDS and VSM techniques, respectively. The results revealed that BiFeO 3 phase with rhombohedral R3c structure with a mean particle size of 40 nm was formed in the sample processed with a Bi 2 O 3 /Fe 2 O 3 molar ratio of 1:1 after calcination at 800 °C. Rietveld analysis which was applied to the x-ray diffraction data via MAUD software indicated high purity of 95%wt for the above sample. Deviation from the stoichiometric molar ratio (Bi 2 O 3 /Fe 2 O 3 : 0.9, 1.1, 1.2) yielded higher content of the intermediate phases of Bi 2 Fe 4 O 9 and Bi 25 FeO 40 . FESEM studies showed that the mean particle size was increased from 40 to 62 nm by increasing calcination temperature from 800 to 850 °C. VSM results for 1:1 molar ratio samples indicated that increasing the calcination temperature from 800 to 850 °C increased saturation magnetization (M s ) from 0.087 to 0.116 emu/g and also coercive field (H c ) from 60 to 100 Oe.
Synthesis of Nanostructured Bismuth Ferrite by Mechano-Thermal Route
Advanced Materials Research, 2014
In this study, multiferroic BiFeO 3 (BFO) powders were synthesized via mechanical activation of Bi 2 O 3 and Fe 2 O 3 with the molar ratio of 1:1, using a planetary high energy ball mill and subsequent heat treatment. All samples were milled for 20 h and heat treated at various temperatures. XRD, FESEM, LPSA, and VSM techniques were used to evaluate the powder particle characteristics. FESEM images of 20 h milled sample indicated plate-like particles with a mean thickness of 45 nm and its LPSA results showed the mean agglomerate size of about 2.0 µm. XRD results of calcined samples showed that the BFO phase began to form at 650 °C and fully formed at 750 °C. In comparison to the conventionally processed samples, BFO phase formation temperature decreases by ∼100 °C in the samples produced by mechanical activation assisted process. VSM measurements of the sample heat treated at 750 °C revealed a saturation magnetization (M s ) of 0.054 emu/g and coercivity (H c ) of 412 Oe.
Journal of Magnetism and Magnetic Materials, 2014
Nanostructured multiferroic Bi (1 À x) Ba x FeO 3 x ¼ 0.0, 0.1, 0.2 were prepared by hydrothermal technique. All samples belonged to the rhombohedrally distorted perovskite structure. The morphology of the particles changed with the doping of barium. Effect of barium doping on the dielectric constant was studied over a wide frequency range of 1000 Hz-1 MHz. The activation energy due to relaxation and due to conduction was measured from the Cole Cole plot and the AC conductivity versus frequency plot respectively. The activation energy estimated from both the studies was close to each other. The activation energy also enhanced with the increase in the barium content. The magnetization at the highest available field ($ 1.6 T) increased from 0.05 emu/g for the sample with x ¼0.0-12 emu/g for the sample with x ¼ 0.2. The magnetic measurements show a significant increase in magnetization around 400 1C. Remnant polarization for x ¼0.0 was negligible and it increased to 0.06 mC/cm 2 for x ¼0.2.
Ceramics International, 2019
Bismuth ferrite, BiFeO 3 , was doped with a wide range of concentrations (0-30%) of Gd in order to investigate structural, ferroelectric, and magnetic properties and their correlation. Powder samples of Bi 1-x Gd x FeO 3 (x = 0.00-0.30) were prepared using the hydro-evaporation synthesis method. Sintering process at 870°C for 6 h of as-prepared, Gd doped BiFeO 3 powders resulted in ceramic samples with relative densities in the range of (74-86) %. XRD analysis revealed that Bi 1-x Gd x FeO 3 samples (x = 0.00-0.09) crystallized in rhombohedral phase; Bi 1-x Gd x FeO 3 samples (x = 0.10-0.20) contained both rhombohedral and orthorhombic phases, while Bi 1x Gd x FeO 3 (x = 0.30) sample contained only the orthorhombic phase. The structural parameters obtained after Rietveld refinement for single-phase Bi 1-x Gd x FeO 3 ceramic samples and microstructure image analysis were correlated with the results of ferroelectric and magnetic measurements. Bi 1-x Gd x FeO 3 (x = 0.0625, 0.075, 0.09) samples showed improved ferroelectric properties and reduced leakage current density in comparison with undoped BiFeO 3. Gradual increase in Gd content in BiFeO 3 led to enhanced magnetic responses and weak ferromagnetic behavior.
Effect of Mn substitution on dielectric and magnetic properties of multiferroic bismuth ferrite
Nanocrystalline powders of bismuth ferrite (BiFeO3) and manganese doped bismuth ferrite (Bi0.95Mn0.05FeO3) were prepared using sol-gel autocombustion method. Structural analysis of these samples using XRD data reveals the existence of rhombohedrally distorted perovskite phase in both the samples. The Mn doping for A-sites in bismuth ferrite improves the surface morphology with uniform grain growth as confirmed by scanning electron micrographs on the samples. The frequency responses of dielectric constant (ε) and dielectric loss tangent (tan δ) have been investigated in a wide range of frequencies at room temperature. Dielectric performance was improved in the manganese doped bismuth ferrite when compared to pure bismuth ferrite. Magnetic studies (M-H loops) were also carried out using vibrating sample magnetometer at room temperature in order to understand the magnetic behaviour of the materials. Significant enhancement in the value of saturation magnetization was found in the manganese doped bismuth ferrite system. The variations in different dielectric and magnetic parameters of the Mn doped bismuth ferrite have been understood in terms of the modified cationic preferences and structural changes. Nevertheless, it can be inferred that the improved results in structural, dielectric and magnetization values in the manganese doped system would obviously make it a good choice for sensors and actuators applications.
Structural, Dielectric, and Magnetic Properties of Ba-Doped Multiferroic Bismuth Ferrite
The main focus of the research was to correlate the microstructure with dielectric and magnetic properties of Bi1-xBaxFeO3 samples. Bi1-xBaxFeO3 samples (x = 0.1, 0.2 and 0.3) were synthesized by the conventional solid-state reaction method using nano-powders of Bi2O3, Fe2O3, and BaCO3. Thereafter, field emission scanning electron microscope and X-ray diffraction (XRD) techniques were used to examine the structure and phase of the samples. Phase analysis by XRD indicated that the single-phase perovskite structure was formed with possible increment in lattice parameter with increasing Ba doping. Complex permeability (l0 i and l00 i ) measured using impedance analyzer confirmed the increase in magnetic property with increasing Ba doping. Finally, dielectric constant (k) was analyzed as a function of temperature at different frequencies. Dielectric constant as high as 2900 was attained in this research for Bi0.8Ba0.2FeO3 sample due to reduction in leakage current at this composition.
Mechanochemical synthesis of bismuth ferrite
2013
A powder mixture of Bi 2 O 3 and Fe 2 O 3 was mechanically treated in a planetary ball mill in an air from 30 to 720 minutes. It was shown that the mechanochemical formation of BiFeO 3 (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 810 o C for 1h followed immediately by quenching process.
Magnetic contributions in multiferroic gadolinium modified bismuth ferrite ceramics
Scripta Materialia, 2020
Bi 0.88 Gd 0.12 FeO 3 multiferroics are of interest for next-generation electronics and are shown with a remnant magnetization 0.2 emu •g −1 , coercive field 8 kOe, Curie temperature 370 °C and magnetization of 0.7 emu •g −1 at magnetic fields 30 kOe. Scanning probe microscopy confirmed the intrinsic multiferroicity in the perovskite phase with coexistence of ferroelectric/ferroelastic and ferromagnetic domain structures. Strong magnetic hysteresis was produced by thermal cycling to 10 0 0 °C due to degeneration of the perovskite phase into iron oxide inclusions, highlighting the importance of processing, thermal history and thermodynamic stability for minimizing the amount of parasitic magnetic secondary phases.
Synthesis and Magnetic Properties of Pure and Cobalt-Doped Nanocrystalline Bismuth Ferrite
MRS Proceedings, 2010
Applications of nanocrystalline multiferroics in sensor development, massive memory storage or in the fabrication of new devices taking advantage of the electron charge and spin explains the need of investigating various options to synthesize these types of materials. Among promising candidates, Bismuth ferrite (BiFeO3) is a multiferroic material that exhibits ferromagnetism, ferroelectricity and ferroelasticity. The present research is focused on the systematic study of the polyol synthesis of substrate-less nanocrystalline BiFeO3 particles and its structural and magnetic characterization. As an attempt to explore the possibility of tuning the ferrite magnetic properties, host BiFeO3 was doped with cobalt ions in the 5at. % -10at. % range. Our results suggested that the ferrite formation and its properties were strongly dependent on both, the annealing conditions of the precursors and the concentration of cobalt species. Well-crystallized pure BiFeO3 was produced after annealing th...