scholarly journals Conventional synthesis of perovskite structured LaTixFe1-xO3: A comprehensive evaluation on phase formation, opto-magnetic, and dielectrical properties

2020 ◽  
Author(s):  
Ramesh Kumar Raji ◽  
Vishista Kurapati ◽  
Tholkappiyan Ramachandran ◽  
M Muralidharan ◽  
R Suriakarthick ◽  
...  
Keyword(s):  
Comprehensive Evaluation ◽  
Lattice Structure ◽  
Orthorhombic Phase ◽  
Spectroscopic Studies ◽  
Chemical Compositions ◽  
Excitonic Absorption ◽  
Substitution Level ◽  
Tan Δ ◽  
Dielectrical Properties ◽  
Ti Substitution

Abstract In the current study, we report a comprehensive evaluation of the microstructures, optical, dielectric and magnetic traits of Ti-substituted perovskite structured lanthanum ferrite with chemical compositions LaTixFe1−xO3 (x = 0, 0.05, 0.15, 0.25). X-ray diffraction with Rietveld refinement and Raman analysis confirmed that both pure and Ti-substituted LaFeO3 maintained single-phase orthorhombic phase with Pbnm symmetry. Fourier transform infrared spectroscopy (FTIR) studies revealed the information about the positions of the ions and their bonds within the lattice structure of the LaFeO3. The spherical shaped morphology of all products was confirmed by SEM. The quantitative chemical composition and their distribution were confirmed by EDAX and mapping. The UV-Vis spectroscopic studies showed an excitonic absorption edge at 590 nm is ascribed to the electronic transition from O2p→Fe3d. Optical band gap (Eg) values were assessed by applying Tauc schemes, showed that Eg values are in a narrow range (1.85–2.02 eV). The dielectric properties such as, dielectric constant (ε’), dielectric loss (tan δ) was examined by varying with temperature and frequency. The magnetic results revealed weak ferromagnetic nature trait at 300 K. The variation in Ms (saturation magnetization), Hc (coercivity) and Mr (remanence) values were observed with increasing Ti substitution level.

Conventional synthesis of perovskite structured LaTixFe1-xO3: A comprehensive evaluation on phase formation, opto-magnetic, and dielectric properties

2021 ◽  
Vol 112 (9) ◽  
pp. 753-765
Author(s):  
Ramesh Kumar Raji ◽  
Tholkappiyan Ramachandran ◽  
M. Muralidharan ◽  
R. Suriakarthick ◽  
Muthu Dhilip ◽  
...  
Keyword(s):  
Single Phase ◽  
Optical Band Gap ◽  
Comprehensive Evaluation ◽  
Magnetic Behavior ◽  
Orthorhombic Phase ◽  
Conventional Solid State Reaction ◽  
Raman Analysis ◽  
Excitonic Absorption ◽  
Magnetic And Dielectric Properties ◽  
Quantitative Chemical

Abstract Perovskite structured LaTixFe1-xO3 (x = 0, 0.05, 0.15, 0.25) lanthanum ferrites were synthesized by conventional solid-state reaction. The structural Rietveld refinement and Raman analysis were conducted and confirmed that single-phase orthorhombic phase with Pbnm symmetry formed. The positions of the ions and their bonds of these ferrites were investigated. The spherical shaped morphology of these ferrites was examined. The quantitative chemical composition and distribution of these ferrites were confirmed. The excitonic absorption edge was observed at 590 nm; ascribed to the electronic transition from O2p→Fe3d and optical band gap values increased from 1.85– 2.02 eV as Ti concentration increased. The dielectric and magnetic behavior of these ferrites was studied. It is suggested that synthesized LaTixFe1xO3 powders with different properties could be tailored for different requirements.

scholarly journals Flux Single Crystal Growth of BaFe12−xTixO19 with Titanium Gradient

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 264
Author(s):  
Vladimir E. Zhivulin ◽  
Evgeny A. Trofimov ◽  
Olga V. Zaitseva ◽  
Dmitry A. Zherebtsov ◽  
Danil A. Uchaev ◽  
...  
Keyword(s):  
Single Crystal ◽  
Barium Hexaferrite ◽  
Solution Growth ◽  
Controlled Cooling ◽  
Substitution Level ◽  
Growth Method ◽  
Ti Substitution ◽  
Relationship Of ◽  
Top Seeded Solution Growth ◽  
The Relationship

Titanium substituted barium hexaferrite BaFe12−xTixO19 single crystal was grown by the top seeded solution growth method from flux on the seed with controlled cooling below 1175 °C. Titanium substitution level gradient in the single crystal in the vertical and horizontal directions was studied. Two planes were cut and polished. A justification for the linear gradient of Ti substitution in a BaFe12−xTixO19 single crystal is proposed; substitution levels in the center and periphery were determined. It was shown that upon growth by the top seeded solution growth method, crystals with a linear Ti substitution level gradient from x = 0.73 to x = 0.77 for a distance of 11 mm along pulling direction were obtained. The study led to the conclusion about the relationship of the gradient and changes in the composition of the nutrient solution.

scholarly journals Reply to Kroll and Schmid-Beurmann's comment on “Water decreases displacive phase transition temperature in alkali feldspar” by Liu et al. (2018)

2020 ◽  
Vol 32 (3) ◽  
pp. 305-310
Author(s):  
Wendi Liu ◽  
Yan Yang ◽  
Qunke Xia
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Alkali Feldspar ◽  
Spectroscopic Studies ◽  
Chemical Compositions ◽  
Factors Affecting ◽  
Displacive Phase Transition ◽  
Redistribution Of Hydrogen ◽  
The Moment

Abstract. It has long been known that hydrogen impurities can be incorporated in the structure of nominally anhydrous minerals (NAMs) and substantially influence their physical properties. One of the geologically most prominent NAMs is feldspar. The hydrogen concentration in NAMs is usually expressed in parts per million of water by weight (ppm H2O wt.) In this paper, we use the term “hydrogen” for uniformity, except when we use “water” for describing its amount expressed as parts per million of H2O by weight. In our article (Liu et al., 2018), we carried out in situ high-temperature X-ray powder diffraction and Raman spectroscopic studies on three natural anorthoclase samples with similar Or (K-feldspar) contents (Ab67Or31An2, Ab66Or31An2, and Ab65Or33An3) and Al–Si disordering but contrasting water contents. The spectroscopic results suggested that the displacive phase transition temperature is higher for the nearly anhydrous anorthoclase sample than the anorthoclase samples with about 200 ppm water, and we thus concluded that hydrogen is another factor impacting the displacive phase transition temperature. We thank Kroll and Schmid-Beurmann for pointing out the weakness in our interpretation that hydrogen is a possible important factor (Kroll and Schmid-Beurmann, 2020). To clarify this issue, we conducted transmission electron microscopy (TEM) experiments on the three samples to check texture effects. The TEM studies indicated that the nearly anhydrous anorthoclase sample consists of two feldspar phases, a K-poor and a K-rich one, and that the K-poor area may be responsible for the higher displacive phase transition temperature. According to the observation that the temperature of redistribution of hydrogen is accordant with the displacive phase transition temperature, the effect of hydrogen could not be ruled out. Based on these results, it can be concluded that hydrogen may not be the sole possible factor, and it was a proposition more than a definitive proof for the moment. Natural feldspars are complex, and factors affecting displacive phase transitions are multiple (e.g., Salje et al., 1991; Harrison and Salje, 1994; Hayward and Salje, 1996; Dobrovolsky et al., 2017). Therefore, to further investigate hydrogen effects on displacive phase transition in feldspar, synthetic samples with pure chemical compositions and hydrogen species are necessary. In the following, we address each issue in the same order as in the comment by Kroll and Schmidt-Beurmann (2020).

Dynamic nanomechanical response of nacre

2006 ◽  
Vol 21 (8) ◽  
pp. 2045-2051 ◽  
Author(s):  
Bedabibhas Mohanty ◽  
Kalpana S. Katti ◽  
Dinesh R. Katti ◽  
Devendra Verma
Keyword(s):  
Mechanical Properties ◽  
Loss Factor ◽  
Dynamic Properties ◽  
Loss Modulus ◽  
Spectroscopic Studies ◽  
Increase With Increase ◽  
Nanocomposite System ◽  
Brick And Mortar ◽  
Tan Δ ◽  
Dynamic Nanoindentation

Nacre, the shiny inner layer of mollusk shells is a model biomimetic nanocomposite system. Its exceptional mechanical properties have been the inspiration for materials scientists for several decades. Nacre exhibits a layered brick and mortar structure. It is composed of 95% inorganic (aragonitic CaCO3) phase and 5% organic (mainly proteins and polysaccharides) phase that are arranged in interlocked brick and mortar architecture with the mineral as bricks and organics as the mortar. In the current work, we describe the dynamic nanomechanical behavior of nacre using dynamic nanoindentation (nano-DMA) experiments. Two sets of loads were applied to obtain the dynamic response from varying depths in nacre. These tests were performed at three different frequencies (25, 50, and 100 Hz) to study the effect of frequency on the dynamic properties of nacre. The loss modulus (E″) and the loss factor (tan δ) were measured. Both of these parameters were observed to increase with increase in depth. Significant increase in tan δ was observed with the increase in frequency. Photoacoustic Fourier transform infrared spectroscopic studies on nacre indicate the presence of water in nacre. This water may be present at nanograin interfaces in nacre platelets, at organic–inorganic interfaces, and also in the organic phase in nacre. We believe that water is one of the significant contributors to the viscoelasticity of nacre. Our results indicate that the aragonite platelets in nacre may also contribute to viscoelasticity.

Evaluation of Tobacco Mixing Uniformity Based on Projection Pursuit

2012 ◽  
Vol 601 ◽  
pp. 128-133
Author(s):  
Jun Li Li ◽  
Jian Lin Mao ◽  
Geng Yun Yin
Keyword(s):  
Evaluation Method ◽  
Comprehensive Evaluation ◽  
Projection Pursuit ◽  
Evaluation Index ◽  
Volatile Acid ◽  
Chemical Compositions ◽  
Total Volatile ◽  
Comprehensive Evaluation Method ◽  
Practical Evaluation ◽  
Overall Evaluation

A new comprehensive evaluation method of tobacco mixing uniformity was presented in this paper. In this method, projection pursuit model was used to select evaluation index and determine the index weights. Seven chemical compositions which had a major impact on the overall evaluation, such as total volatile acid, total volatile bases, PH, polyphenol, protein, total nitrogen and chlorine were sampled repetitiously and calculated the average and coefficient of variance. Tobacco mixing uniformity was evaluated by the score according to coefficient of variance. Comprehensive evaluation of five batches of tobacco was carried out and the results were consistent with the traditional. This method was easy to get basic data and evaluation results fitted the actual. It was a simple and practical evaluation method of mixing uniformity.

DIELECTRIC PROPERTIES OF Li-Sb FERRITES

2005 ◽  
Vol 19 (18) ◽  
pp. 899-905 ◽  
Author(s):  
SHIVAJI CHONGTHAM ◽  
SUMITRA PHANJOUBAM ◽  
H. N. K. SARMA ◽  
RADHAPIYARI LAISHRAM ◽  
CHANDRA PRAKASH
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Loss Tangent ◽  
Room Temperature ◽  
Substitution Level ◽  
Higher Temperature ◽  
Tan Δ ◽  
Almost All ◽  
Frequency Curves

Dielectric properties such as dielectric constant (ε′) and dielectric loss tangent ( tan δ) of Li 0.5+x Fe 2.5-2x Sb x O 4 ferrites, 0.10≤ x ≤0.30 in steps of 0.05 have been investigated as a function of composition, frequency and temperature. The dielectric constant showed dispersion with frequency in the range of 100 Hz–1 MHz. Peaks were observed in the tan δ versus frequency curves for almost all the samples. The temperature variation of dielectric constant for the different samples was studied at 10 kHz in the temperature range from room temperature to 433 K. Peaks were observed for some of the samples. The peaks were seen to shift towards higher temperature region as the substitution level increases. The mechanisms involved in the processes are discussed in this paper.

Behavioral Study of IN-718 Due to High Pressure Shock Wave Loading in Contact Geometry

2009 ◽  
Author(s):  
Ashok K. Sharma
Keyword(s):  
New Technology ◽  
Dendritic Structure ◽  
Spectroscopic Studies ◽  
Sem Analysis ◽  
Chemical Compositions ◽  
Wave Loading ◽  
Properties And Characterization ◽  
Post Shock ◽  
Super Alloy

Shock waves when propagate through materials produce sudden changes of pressure and temperature which result in the production of new phases/transformations. This paper describes the experimental work for the shock synthesis of IN 718 with unique properties and characterization of its pre and post shock compacts by spectroscopic methods. Super alloy powders of IN 718 of various chemical compositions and unique physical properties have been shock compressed to develop a new technology. From the spectroscopic records, intensity of reflected beam at a particular angle, the spacing between parallel planes, the lattice constant, the radius of an atom, FWHM value for each peak, etc. have been analyzed to investigate the unique properties of shock compacts. No porosity has been observed in the shock compacted specimens. On retrieval of samples from the compaction systems, the specimens are subjected to chemical composition, stress analysis and various other spectroscopic studies. The dendritic structure has been clearly observed in the centre with dendrites oriented in the radial direction which also happens to be the direction of heat flow. SEM analysis has indicated that the crystalline structure is intact in the shock compressed specimens.

scholarly journals Spectroscopic studies of kaolin from different Brazilian regions

Clay Minerals ◽  
2008 ◽  
Vol 43 (1) ◽  
pp. 129-135 ◽  
Author(s):  
R. B. Scorzelli ◽  
L. C. Bertolino ◽  
A. B. Luz ◽  
M. Duttine ◽  
F. A. N. G. Silva ◽  
...  
Keyword(s):  
Paper Industry ◽  
Spectroscopic Studies ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Chemical Treatments ◽  
Fe Oxides ◽  
Spin Resonance ◽  
Before And After ◽  
Mineralogical Phase

AbstractOver the past several decades, kaolin has been used intensively in the paper industry as a coating and filler material. These applications require kaolin of a high brightness grade, which depends heavily on the level of impurities (mainly Fe-bearing minerals such as Fe oxides and hydroxides) and may be improved by beneficiation processes involving grain-size classification, magnetic separation and chemical treatments. This investigation was carried out on five Brazilian kaolin samples of different geographical and geological origins. Granulometric, mineralogical, chemical and physical characterizations were performed on all samples before and after the beneficiation process.Chemical compositions were determined by X-ray fluorescence and the most important crystalline phases were identified using X-ray diffraction. Kaolinite is the dominant mineralogical phase with minor amounts of muscovite and quartz. The nature of Fe impurities was investigated by electron spin resonance and 57Fe Mössbauer spectroscopy. For all studied kaolin samples, Fe ions (Fe3+ and Fe2+) are present in variable amounts, in the kaolinite structure and also in Fe oxides (magnetite, hematite and goethite). The beneficiation procedure aims to remove these Fe oxides and was found to be most efficient for the Mogi das Cruzes kaolin. The Seridó kaolin had the best whiteness index observed among the analysed samples.

Structural and Electrical Investigations of Ferroelectric Lead Strontium Titanate Thin Films and Ceramics

2003 ◽  
Vol 784 ◽  
Author(s):  
M. Jain ◽  
P. Bhattacharya ◽  
Yu. I. Yuzyuk ◽  
R. S. Katiyar ◽  
A. S. Bhalla
Keyword(s):  
Thin Films ◽  
Strontium Titanate ◽  
Room Temperature ◽  
Powder Processing ◽  
Lattice Structure ◽  
Spectroscopic Studies ◽  
Cubic Phase ◽  
Raman Spectroscopic ◽  
Structure Changes ◽  
Ceramic Targets

ABSTRACTLead strontium titanate (PbxSr1-xTiO3) (x=0.3–1.0) ceramic targets were prepared by the conventional powder-processing method. Thin films of these compositions were deposited on platinized silicon substrates by pulsed laser deposition technique. X-ray diffraction studies of the ceramic targets showed that the lattice structure changes from tetragonal to cubic phase with the increase of Sr content in PbTiO3. Raman spectroscopic studies of PbxSr1-xTiO3(PST) ceramics and thin films showed that the soft mode decreases to lower frequency and finally disappear at around 60–70 at% Sr content, which confirms the tetragonal to cubic phase transition at room temperature. Dielectric constant measured for PST thin films was in the range of 900–1500 at 1 MHz, with maximum value obtained for PST30 thin film. The loss tangents at room temperature were in the range of 0.07–0.1 for PST thin films with different compositions.

scholarly journals Spectroscopic studies of stellar populations in globular clusters and field stars: Implications for globular cluster and Milky Way halo formation

2019 ◽  
Vol 14 (S351) ◽  
pp. 241-250
Author(s):  
Raffaele Gratton
Keyword(s):  
Globular Clusters ◽  
Second Generation ◽  
Massive Stars ◽  
Stellar Populations ◽  
Spectroscopic Studies ◽  
Chemical Compositions ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Massive Clusters ◽  
Fast Rotating

AbstractWe review spectroscopic results concerning multiple stellar populations in globular clusters. The cluster initial mass is the most important parameter determining the fraction of second generation stars. The threshold for the onset of the multiple population phenomenon is 1–3×105 M⊙. Nucleosynthesis is influenced by metallicity: Na/O and Mg/Al anti-correlations are more extended in metal-poor than in metal-rich clusters. Massive clusters are more complex systems than the smaller ones, with several populations characterized by different chemical compositions. The high Li abundance observed in the intermediate second generation stars strongly favours intermediate mass AGB stars as polluters for this class of stars; however, it is well possible that the polluters of extreme second generation stars, that often do not have measurable Li, may be fast rotating massive stars or super-massive stars. The mass budget factor should be a function of the cluster mass, and needs to be large only in massive clusters.

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