Raman studies of rod-like bismuth strontium manganites (original) (raw)
Studies on rod shaped bismuth strontium manganite ceramics
Rods of Bi 1−x Sr x MnO 3 (BSM) (0.20 ≤ x ≤ 0.50) having different dimensions were synthesized by the solid state reaction method. The replacement of bismuth by strontium in BSM plays an important role in changing the cell volume, and DC resistivity. The surface morphology varied with strontium content and changes from cubic to rods of different sizes. The room temperature resistivity of BSM decreases with strontium from 0.21 M cm to 0.11 M cm. These manganites follow the Arrhenius equation. The thermistor constant increases with Sr content from ∼ 793 K to 1735 K, the maximum being for x = 0 20 and minimum for x = 0 50.
Structural mechanical properties of Sr doped Bismuth manganites
Bismuth strontium manganites Bi 1 -x Sr x MnO 3 (0.20 ≤ x ≤ 0.50) belonging to the orthorhombic structural family were prepared in furnace using a solid state reaction technique. Thick films of Bi (1 -x) Sr x MnO 3 were prepared by simple screen printing route. X ray diffraction data suggest that the synthesized materials have an orthorhombic structure. For synthesized materials, texture coefficient (TC), dislocation density (ρ D ), density of crystallites per unit area (ψ), and mechanical properties are reported along with the influence of x on the structure and mechanical properties of BiMnO 3 thick films.
Microwave Studies of Bismuth Strontium Manganite Thick-Films by Superstate Method
We report structural and microwave properties of rod shaped bismuth strontium manganite , thick-films prepared by screen printing method. The orthorhombic phase formation was confirmed by XRD. The micro rods like morphology and grain size were observed by using SEM analysis. Modification in microstripline properties like microwave absorption , transmittance, and effective dielectric constant which is being done by simple superstrate Bi 1−x Sr x MnO 3 (BSM) thick-films at very high frequencies (microwaves). The effective dielectric constant is due to superstrate, which lies in between 10.41 to 29.22 for thick films.
A Bismuth Manganite with the “2212” Structure: Bi2−xPbxSr1.5Ca1.5Mn2O9−δ
Journal of Solid State Chemistry, 1997
A manganite Bi 2؊x Pb x Sr 1.5 Ca 1.5 Mn 2 O 9؊ , with the 2212 structure, has been synthesized for the first time. Its structural study by powder X-ray diffraction and by electron microscopy has been performed for two compositions, x ؍ 0.5 and x ؍ 1. The average structure consists of double perovskite layers (P) involving MnO 6 octahedra and MnO 5 pyramids intergrown with distorted triple rock salt layers (RS). The perovskite cages are mainly occupied by strontium so that these phases can be formulated [Bi 2؊x Pb x Ca 1.33 Sr 0.67 ] RS [Sr 0.83 Ca 0.17 ] P Mn 2 O 9؊. The HREM investigation shows that the composition x ؍ 0.5 exhibits an incommensurate modulated structure similar to that observed for the superconducting bismuth cuprate and for the iron-based 2212 compound. In contrast, the composition x ؍ 1 does not exhibit any modulation. Although they are rare, some extended defects are observed especially for BiPbSr 1.5 Ca 1.5 Mn 2 O 9؊. Both oxides are semiconductors.
Ferroelectrics, 2003
Raman spectra and pyroelectric studies in bismuth doped SrTiO 3 ceramics, with general formulae Sr (1−1.5x) Bi x TiO 3 , were undertaken. For x = 0.0053, the low frequency Raman spectra exhibit striking similarities with the spectra of the undoped ceramics also revealing the existence of a polar soft-mode TO 1 , that obeys the classical Cochran softening law. The sample with x = 0.133 presents a very different dynamics, and its Raman spectra give evidence for the inexistence of an anti-ferrodistorsive phase transition, that occurs in the undoped ceramics at 104 K. Pyroelectric measurements disclose the existence of small electrical dipoles probably due to polar grain boundaries, off-centre positions of Bi 3+ and Ti 4+ ions, and Sr vacancies, that strongly influence the behaviour of these systems with temperature variation. There is a strong evidence for the existence of a relaxor state in the x = 0.133 ceramic at low temperatures. Keywords: Ferroelectric relaxor; quantum paraelectricity; Raman spectra; pyroelectric current [405]/49 50/[406] A. ALMEIDA et al.
Multiferroic bismuth manganite prepared by mechanochemical synthesis
Journal of the European Ceramic Society, 2010
Multiferroic bismuth manganite (BiMnO 3) is known as a material that exhibits both ferromagnetic and ferroelectric properties making it interesting for various technological applications. Unfortunately, preparation of BiMnO 3 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 BiMnO 3 was prepared for the first time by mechanochemical synthesis in a planetary ball mill. A mixture of Bi 2 O 3 and Mn 2 O 3 was intensively milled in air atmosphere, using stainless steel vials and balls. According to analysis of XPRD results BiMnO 3 obtained after milling for 240 min has a tetragonal structure with lattice parameters a = 3.9230 Å, c = 3.920 Å 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.
J Solid State Chem, 1998
A manganite with a ''tubular'' structure derived from the 2201-type, Bi 3.6 Sr 12.4 Mn 8 O 28؉ , has been synthesized. Its complex crystal chemistry has been studied using XRD, ND, and HREM techniques. It crystallizes in an orthorhombic cell, space group Pbnb, with a ؍ 5.4946 A s , b ؍ 23.595(1) A s , and c ؍ 23.580(1) A s. This structure can be described as an intergrowth, along b, of two types of (010) slices: ''2201''-type slices [Bi 2 Sr 2 MnO 6 ] that are two octahedra thick and manganesedeficient perovskite-related slices [Sr 8 Mn 6 O 16؉ ] that are one octahedron thick. A similar stacking is observed along c, which endows the structure with a pseudotetragonal character. Another way to describe this structure is to consider criss-crossing layers of manganese polyhedra forming tubes, where the [BiO] rows are inserted, and oxygen-deficient pillars, built up of four Mn polyhedra. This phase represents the n ؍ 2 member of a new ''tubular'' family [Bi 2 Sr 2 MnO 6 ] n [Sr 8 Mn 6 O 16؉ ]. Intergrowth and shearing mechanisms arise along the b and c directions, in agreement with the pseudotetragonal character of the structure. The investigation of the transport and magnetic properties of this new manganite shows that it is an insulator and exhibits weak antiferromagnetism at low temperature (p ؍ ؊650 K); the high-temperature data evidence an effective magnetic moment of 4.7 B characteristic of high-spin Mn 3؉ (th ؍ 4.9 B).
Bismuth strontium manganites (BSM) with variation in strontium content have been synthesized by simple solid state reaction method. X-ray diffraction data show that the samples have orthorhombic structure with crystallite size ~40 to 60 nm. SEM studies reveal morphology of micro-rods and micro-flakes. The dielectric constant (ε') and the dielectric loss (tan δ) decreases with the strontium content and the applied frequency which has been attributed to Maxwell-Wagner polarization. The microwave conductivity of samples decreases from 8.9 S/cm to 2.29 S/cm at 8.2 GHz as strontium increases. The penetration depth has also been reported at microwave frequencies from 8 -18 GHz.
Journal of Nanoparticle Research
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 ~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.
Synthesis of Manganese doped Bi2S3 Crystal in Gel method and its thermal Characterisations
International Journal of Scientific Research in Science and Technology, 2022
Manganese doped Bismuth tri sulphide crystals are synthesising using simple gel technique at ambient temperature. X Ray Diffraction analysis was done to determine the structure. Orthorhombic crystal structure was found of grown crystal. FTIR method was utilized for the analysis of various functional groups present in the complex Thermal properties of the crystal was studied by TGA was Discussed .Effect of Doping, and concentration of reactants.
Bismuth manganese titanate: Crystal structure and properties
Solid State Ionics, 2012
Manganese-containing bismuth titanate solid solutions with a pyrochlore-type crystal structure were obtained by the ceramic technique over a wide range of compositions. The NEXAFS (near-edge X-ray absorption fine structure) spectra of Mn2p-absorption in bismuth manganese titanate pyrochlores point to manganese being mainly in the oxidation state + 2 in these solid solutions. The Mn-rich bismuth titanate pyrochlores showed a superposition of antiferro-(long-order) and ferromagnetic (short-order) behavior. The results of impedance investigations show the electron-ionic conductivity in these samples.
2021
Production of nanomaterials by mechanochemical synthesis is one of the important modern methods in new technology. Mechanochemical technique followed by heat treatment has been used to produce bismuth-manganese oxide from bismuth oxide and manganese dioxide. X-Ray Diffraction (XRD) analysis is conducted evaluate the structure changes during the mechanochemical process. Structure transformation from crystalline to complete amorphous phase was observed after short time of milling. The amorphization mechanism and reaction kinetics are examined in the light of the processing parameters and materials composition. Interdiffusion and distraction of the long rang order structure are the proposed mechanisms for amorphization. Bismuth manganese oxide phase with chemical formula Bi2Mn4O10 was formed after heat treatment at 1073 K. Bi2Mn4O10 partially decomposed to γ-Bi12.8O19.2 and α-Mn2O3. Crystallite size (47.6–102.4 nm) of the formed phases after heat treatment is significantly affecting th...
X-Ray Scattering Analysis of Complex Manganites Bi Me Mn O (Me- Ca, Ba, Sr)
2013
Complex oxide phases of compositions Bi CaMn O , Bi SrMn O and Bi BaMn O were synthesized 2 4 10 2 4 10 2 4 10 by high temperature solid state reaction. The structure of the manganites, types of the crystal lattices, parameters of the unit cells, radiographic and pycnometric densities were identified by X-ray scattering for a first time: Bi CaMn O - a=5,68, c=23,2 A, V = 748,2 A , Z=2, = 4,52, =4,55 g/cm , Bi SrMn O - 2 4 10 un.cell rad picn 2 4 10 33
The Synthesis and Characterization of Sol-Gel-Derived SrTiO3-BiMnO3 Solid Solutions
Crystals
In this study, the aqueous sol-gel method was employed for the synthesis of (1−x)SrTiO3-xBiMnO3 solid solutions. Powder X-ray diffraction analysis confirmed the formation of single-phase perovskites with a cubic structure up to x = 0.3. A further increase of the BiMnO3 content led to the formation of a negligible amount of neighboring Mn3O4 impurity, along with the major perovskite phase. Infrared (FT-IR) analysis of the synthesized specimens showed gradual spectral change associated with the superposition effect of Mn-O and Ti-O bond lengths. By introducing BiMnO3 into the SrTiO3 crystal structure, the size of the grains increased drastically, which was confirmed by means of scanning electron microscopy. Magnetization studies revealed that all solid solutions containing the BiMnO3 component can be characterized as paramagnetic materials. It was observed that magnetization values clearly correlate with the chemical composition of powders, and the gradual increase of the BiMnO3 conte...
Materials Today: Proceedings, 2018
Cr, Mg optical ceramics were prepared by the solid-state reactive sintering method within the temperature range of 1750-1800 � C. The influence of the sintering temperature on the microstructure, phase composition, and optical properties of YAG:Cr, Mg ceramics was studied. It has been shown that optimal obtaining temperature of YAG:Cr, Mg ceramics doped with 0.5 аt.% of chromium ions and 0.5 аt.% of magnesium ions is 1765 � C. YAG:Cr, Mg ceramics sintered at T ¼ 1765 � C possess the lowest porosity and optical losses in the visible wavelength range. They are characterized by the average grain size of about 3 μm and in-line transmittance above 80%. Thermal annealing of ceramics results in transition of a part of Cr 3þ ions to Cr 4þ charge state. A decrease in concentration of Cr 4þ ions in tetrahedral coordination with increase the sintering temperature has been observed. This effect was attributed to different charge compensation mechanisms of Mg 2þ ions taking place in YAG:Cr, Mg ceramics obtained at various temperatures. Finally, laser performance of YAG:Cr, Mg ceramics was estimated in the passive Q-switch mode.
Manganite Synthesis By Different Methods
Oriental Journal of Chemistry
Nanostructural dysprosium manganite doped with bismuth, synthesized by three methods: solid-phase, sol-gel and citrate-nitrate. The composition of the synthesized powders was compared to determine the optimal technique. Using X-ray diffraction, the influence of annealing conditions on the structure of manganite was studied. The result of XRD showed that manganite, synthesized variants of methods has orthorhombic structure.
Raman spectroscopy on cubic and hexagonal SrMnO3
Journal of Raman Spectroscopy, 2006
We report on the first optical characterization of both cubic and hexagonal SrMnO3. Roomtemperature Raman spectra collected by means of a micro-Raman spectrometer are shown. The spectrum of the cubic compound is characterized by weak and broad bands in agreement with group-theory which predicts no Raman-active phonons for this compound. On the other hand, the spectrum of the hexagonal compound shows six narrow peaks ascribed to one-phonon processes. A complete polarization analysis of the spectra collected from a single crystallite allows us to completely assign the symmetries of the six observed peaks. Atomic displacements for each phonon peaks are also proposed.