Fe-rich Region Research Articles

Thermodynamics of the α-FeOOH (goethite)-ScOOH solid solution

Scandium (Sc) is a rare element that finds uses in modern technologies. Thermodynamic properties of Sc phases could help in the development of innovative technologies to extract Sc from mining waste. In this work, we investigated the FeOOH–ScOOH solid solution with the goethite structure. The end members and five intermediate compositions were synthesized and characterized. The lattice parameters show that the solid solution is non-ideal, with complex behavior induced by the Fe–Sc substitution. The excess unit-cell volume deviates negatively for the Sc-rich region, and positively for the Fe-rich region from the ideal behavior (Vegard’s law). Enthalpies of dissolution were determined by acid-solution calorimetry in 5 mol·dm-3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\cdot \\hbox {dm}^{-3}$$\\end{document} HCl at T = 343.15 K. Enthalpies of mixing (ΔmixH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta _{mix}H$$\\end{document}), calculated from the experimental data, are small and positive. The available data allow for fitting the data as ΔmixH=Wx(1-x)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta _{mix}H = W x (1-x)$$\\end{document}, with the mixing parameter W=15.2±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$W = 15.2\\pm$$\\end{document}1.0 kJ·mol-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\cdot \\hbox {mol}^{-1}$$\\end{document}. Using ΔfGo\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta _fG^o$$\\end{document} of ScOOH from earlier literature, we calculated a Lippmann diagram that shows that Sc should strongly partition into the aqueous phase upon goethite precipitation. The field observations from lateritic profiles show that Sc is primarily harbored by goethite via adsorption. It seems that under weathering conditions, thermodynamically driven partitioning of Sc3+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {Sc}^{3+}$$\\end{document} into the aqueous phases and its subsequent adsorption onto goethite surfaces controls the mobility of Sc in the weathering profiles.

Indirect magneto-ionic effect in FeSi2/Si nanocomposite induced by electrochemical lithiation and delithiation

A nanocomposite consisting of iron disilicide nanocrystals embedded in a Si matrix was prepared from industry-grade ferrosilicon by ball milling and subsequent heat treatment. By tailoring the heat treatment temperature either the metallic α-FeSi2 or the semiconducting β-FeSi2 phase could be made the dominant one, as indicated by x-ray diffraction. Magnetization curve and zero-field cooled/field cooled measurements revealed that ferromagnetic and superparamagnetic centers are present in the nanocomposites, which could be attributed to Fe-rich defective regions at the surface of the iron disilicide nanocrystals. For both nanocomposites, containing either mainly the α or β phase, we could show that the magnetization can be varied by about 40% by electrochemical lithiation and delithiation of the surrounding Si matrix, with up to 6.5% of the magnetization change being reversible. These variations could be attributed to the formation of additional Fe-rich magnetic regions, induced by a local change of the Fe/Si fraction at the FeSi2/Si interfaces, and their subsequent partial elimination. Thus, this work demonstrates a new concept for how an ‘indirect magneto-ionic effect’ can be obtained in composite materials consisting of a phase prone to the electrochemical ion uptake (i.e. the Si matrix) and a magnetic phase (i.e. the FeSi2 nanocrystals).

Mӧssbauer and dielectric studies of Bi0.6Nd0.4Fe0.5M0.5O3 (M – Mn, Cr) solid solution ceramics fabricated by a high-pressure synthesis

Bi0.6Nd0.4Fe0.5M0.5O3 (M – Mn, Cr) compositions with perovskite structure were fabricated by a high-pressure synthesis. Mӧssbauer studies have shown that doping with Nd does not change substantially Neel temperature values of Bi0.6Nd0.4 Fe0.5M0.5O3 (M – Cr, Mn) compositions. However, the Fe3+ and Mn3+ ions seem to be inhomogeneously distributed in the crystal lattice and form Fe-poor and Fe-rich regions. Similar result was obtained by us earlier for Bi(Fe1-xCrx)O3 solid solution. Both compositions studied exhibit a giant dielectric response in a wide temperature range. The giant dielectric response seems to be due to the relaxation of electrons or polarons trapped by oxygen vacancies.

A novel high-temperature FeSiAl/CaO–B2O3–SiO2 microwave absorption coating prepared via atmospheric plasma spraying

In this paper, CaO–B2O3–SiO2 (CBS) is utilized as matrix material of microwave coating for the first time to achieve high-performance microwave absorption under high-temperature. A series of FeSiAl (FSA)/CBS composite coatings were prepared via atmospheric plasma spraying. The impact of spraying power on the microstructure, electromagnetic properties, and high-temperature stability of as-sprayed coatings were studied. The experimental results reveal that CBS could effectively suppress the formation of the lamellar structure of FSA as the low initial melting temperature, also form unexpected Fe2SiO4 structure with FSA during the spraying process. The increase in complex permittivity of the coating is primarily attributed to enhanced coating density and the development of Fe-rich regions within the CBS matrix. Furthermore, the dense coating prevents the oxidation of FSA and exhibits high-temperature stability. Our coating of 1 mm thickness has a reflection loss below −5 dB with frequency range of 7–14.8 GHz at 500 °C.

Reduction-Induced Magnetic Behavior in LaFeO3-δ Thin Films.

The effect of oxygen reduction on the magnetic properties of LaFeO3-δ (LFO) thin films was studied to better understand the viability of LFO as a candidate for magnetoionic memory. Differences in the amount of oxygen lost by LFO and its magnetic behavior were observed in nominally identical LFO films grown on substrates prepared using different common methods. In an LFO film grown on as-received SrTiO3 (STO) substrate, the original perovskite film structure was preserved following reduction, and remnant magnetization was only seen at low temperatures. In a LFO film grown on annealed STO, the LFO lost significantly more oxygen and the microstructure decomposed into La- and Fe-rich regions with remnant magnetization that persisted up to room temperature. These results demonstrate an ability to access multiple, distinct magnetic states via oxygen reduction in the same starting material and suggest LFO may be a suitable materials platform for nonvolatile multistate memory.

Enhancing Surface Properties of Cu-Fe-Cr Alloys through Laser Cladding: The Role of Mo and B4C Additives

Laser cladding is a powerful surface treatment technique that can significantly enhance the properties of metal alloys. This study delves into the liquid phase separation behavior of Cu-Fe-Cr alloys under the rapid solidification conditions inherent in laser cladding and evaluates the influence of 4% Mo and 2% B4C additions on the resulting alloy characteristics. The intensive undercooling characteristic of the laser cladding process facilitates the alloy’s entry into the liquid-phase immiscibility gap, prompting pronounced phase separation. Our investigation reveals the emergence of Fe-rich regions, exhibiting a variety of shapes, set against a continuous Cu-rich matrix. The incorporation of Mo and B4C was found to modulate the mixing enthalpy and entropy, thereby refining the phase distribution: Mo was observed to prevent the agglomeration of Fe cores, resulting in a dispersion of isolated Fe cores throughout the Cu-rich matrix, while B4C promoted a more uniform compositional distribution. This study further enumerates the enhancements in microhardness, wear resistance, and magnetic properties of the alloys. Notably, the Cu-Fe-Cr-Mo-B4C alloy demonstrated a microhardness exceeding 600 HV, a low coefficient of friction around 0.15, high saturation magnetization, and reduced coercivity. These results underscore the efficacy of laser cladding in tailoring the microstructure and properties of Cu-Fe alloys, providing insights for the controlled manipulation of phase separation to optimize surface characteristics for engineering applications.

Effect of a ring-shaped laser beam on the weldability of aluminum-to-hilumin for battery tab connectors

Advances in laser beam shaping technologies are being studied and are considered beneficial in many aspects of dissimilar metal joining, which include reducing intermetallic compounds (IMCs), optimizing weld pool profiles, and controlling porosity and spatters. This paper utilizes a coaxial ring and core dual beam laser and aims to study the impact of the power ratios between core and ring beams on the weldability of 1100 aluminum alloy to hilumin (steel). High-resolution electron microscopy was performed in the cross sections of the weld pools to quantify the melt pool composition and subsequent IMC formation and weld defects (cracking and cavitation). Lap-shear mechanical testing and electrical resistivity testing were also carried out. Results showed that the optimal power ratio for lap-shear strength was 0.4 (intermediate core and ring) due to the reduction in the Fe-rich liquid into the upper weld region. As a result, this produced a smaller interface between the Fe-rich region and Al, thus reducing the formation of the most detrimental IMC (e.g., Fe2Al5). Conversely, a power ratio of 0.2 (core-dominant) was found beneficial for reducing electrical resistance due to a reduced total IMC volume.

Correlated microstructure and magnetic properties of Ce-substituted sintered Nd-Fe-B magnets: Role of various phases at triple junctions and grain boundaries

We report the investigation of the microstructure and magnetic properties of a sintered (Nd,Pr)30.3-xCexFebalM1.4B0.92 (in wt.%, xCe = 0) magnet with varying Ce substitutions (xCe = 2, 4, 6, 8). Structure analysis revealed a lattice contraction with Ce addition of up to xCe < 6, and the further increase in the Ce content to 6 wt.% led to a suppression in lattice contraction. The magnetic properties showed a notable deviation from the linear trend in coercivity and remanent magnetization for the magnets with Ce content of xCe > 4. The detailed microstructure analysis revealed that the magnets with xCe > 4 exhibit the REFe2 phase at the expense of a reduced mass fraction of a REOx phase, suggesting that the generation of the REFe2 phase suppressed the formation of the REOx phase. The site occupancy and valence state of Ce, analyzed using atomic-resolution energy dispersive spectroscopy and electron energy loss spectrometry, established that the suppressed lattice contraction is accompanied by a preferential site occupation of Ce from a random case to a 4f-centric site, along with a valence change from a mixed state to a trivalent state, inferring that Ce3+ ions are rejected from the 4g site of the RE2Fe14B phase to occupy the 4f site with a subsequently reduced number of Ce4+ ions due to the magneto-volume and chemical bonding effects. These findings display a new phase formation pathway of the REFe2 phase from a valence state perspective, i.e., the part of Ce4+ ions is considered to be rejected from the RE2Fe14B phase to nucleate the REFe2 phase, which is later found to separate chemically into RE-rich and Fe-rich regions. Further, a bi-layer interfacial structure, composed of Fe-rich and RE-rich layers, is formed in between the RE2Fe14B and the REFe2 phases due to the weak wettability of the REFe2 phase and a slightly positive mixing enthalpy between Ce and Fe. The deviation in magnetic properties is discussed based on the structural and microstructural results. These findings provide structural insight for developing low-cost and high-performance Ce-substituted Nd-Fe-B magnets.

Towards high-strength, high-ductility ferritic steels: Pathways to overcome the “475 °C embrittlement” in spinodally decomposed Fe-40Cr alloy

Fe–Cr is a model alloy for ferritic steels used in thermal power generation systems and envisaged as primary structural material for future fusion reactors. However, upon heating and, further, under irradiation, Fe–Cr can suffer from phase decomposition leading to the formation of Fe-rich and Cr-rich regions that induce simultaneous hardening and embrittlement. In this study, we examine the origins of the degradation in mechanical properties by performing room-temperature in situ micropillar compression tests on single-crystalline Fe–40wt.%Cr alloys in solid solution, and in the spinodally decomposed state obtained after annealing at 500 °C for 1008 and 2016 h, respectively. The compressed micropillars are subjected to correlative nanoscale structural characterization using transmission electron backscattered diffraction and transmission electron microscopy. Dislocation slip occurs unequivocally on the {110}〈11¯1〉 slip system for all conditions. While the 2016 h annealed state exhibits a more evolved nanoscale phase modulation than the 1008 h annealed condition, both microstructures display approximately double the yield strength of the solid-solution state without any concurrent loss of ductility. Our findings reveal a fundamental change in plasticity mechanism across the three different microstructures. Deformation in the solid-solution state is associated with kink-mediated local plasticity occurring on multiple glide systems, which activate sequentially based upon the largest instantaneous Schmid factor. This gradually transforms into a less localized Lüders-band like plasticity associated with single-slip activation in the 1008 h annealed state, while the deformation in the 2016 h annealed state is marked by uniform strain hardening related to a homogeneous polycrystalline-like dislocation motion occurring simultaneously on multiple slip systems. Correlations between the spatial and compositional fluctuations in Cr and the associated plasticity dynamics are established. It is shown that the spatial fluctuations in Cr strongly influence dislocation strengthening and the relative mobility of the edge and screw components across all microstructural states. It is further concluded that the phase-separation effect, despite promoting strengthening, does not act as the primary cause of embrittlement, but rather plays a contrary role of enhancing ductility.

Co-evolution of the atomic/nano scale structural heterogeneities and magnetic properties of Fe-Si-B-Cu metallic glass during relaxation with composition fluctuations

The metallic glass (MG) exhibits composition fluctuation or chemical heterogeneity during relaxation. However, the influence of this factor on the evolution of the intrinsic structural heterogeneity of MGs remains unclear. In this study, we systematically examined the co-evolution between atomic and nano-scale structural heterogeneities of Fe-Si-B-Cu MGs during relaxation. We discovered that, despite some degree of fluctuation in composition during the relaxation of Fe-Si-B-Cu MGs, it does not prevent the reduction of structural heterogeneities at the atomic/nano scale. The results demonstrate an overall increase in the number density and number of types of densely packed clusters with a high degree of local five-fold symmetry and a decrease in the number density and number of types of loosely packed clusters with a low degree of local five-fold symmetry. Furthermore, a certain degree of compositional fluctuation during relaxation of Fe-Si-B-Cu MGs facilitates the formation of uniformly distributed Fe-rich regions and Cu-rich regions.

Understanding magnetic interactions and reversal mechanisms in a spinodally decomposed cobalt ferrite using first order reversal curves

Cobalt ferrites exhibit widely varied magnetic behaviour due to the presence of a miscibility gap leading to the formation of periodic self-assembled nanostructures via spinodal decomposition. Periodicity and amplitude of the compositional fluctuations can be controlled by thermodynamic and kinetic processing parameters which allows for careful tuning of the magnetic properties. Although reports have shown evidence of spinodal decomposition, there is a lack of detailed characterization of the magnetic interactions and reversal mechanisms in these materials. In this work we use high-resolution first order reversal curves (FORC) measurements to understand the underlying magnetic processes occurring in a cobalt ferrite with a nominal composition of Co1.8Fe1.2O4 before (calcined) and after spinodal decomposition (annealed). Additionally, FORC measurements with preconditioning fields were conducted to separate the interaction signatures at low coercive fields by biasing the sample in positive and negative mean fields. Microstructural characterization using TEM combined with EDS showed uniform chemistry in the calcined sample and the presence of Fe rich and Co rich regions in the annealed sample, due to spinodal decomposition. Signs of positive exchange interactions were observed in both calcined and annealed samples. This work presents the first detailed magnetic characterization of magnetic interactions in a nanostructured cobalt ferrite, and provides an example of magnetic characterization of nanostructured ferrites using FORC.

Thermodynamic reassessment of Fe–Nb–V system

Thermodynamic reassessment of the ternary Fe–Nb–V system was carried out after a critical review of the available experimental and ab initio data. The primary solidified phases of Fe–Nb–V alloys were investigated using scanning electron microscopy and X-ray diffraction analysis. The C14 Laves phase exhibits a wide primary solidification field in the Fe-rich region, which is in contradiction with the experimental observation in the literature. Ab initio calculations were performed to obtain the enthalpies of formation of three intermetallic compounds (i.e., C14 Laves, μ, and σ), which were used to estimate the thermodynamic parameters. The end-member parameters for the three phases were improved in comparison with the previous description. The presently obtained thermodynamic description of the ternary system can reproduce the wide homogeneity range of the C14 Laves phase and the phase equilibria between the intermetallic compounds and bcc phase.

Experimental study of Fe-rich region in the Fe–Nb–Zr system at 1000 °C

The Fe-rich corner of the Fe–Nb–Zr phase diagram was studied at 1000 °C by using synchrotron x-ray powder diffraction (SXPD) technique and quantitative electron probe microanalysis (EPMA). The MgCu2 (C15) and MgZn2 (C14) structures corresponding to Fe2Zr and Fe2Nb Laves phases were observed in the Fe2Zr–Fe2Nb pseudo-binary system. The MgNi2 (C36) structure corresponding to Fe2(Zr1-xNbx) Laves phase was not found in any of the compositions explored at this temperature. The existence of two three-phase fields (C15 + Fe23Zr6 + C14) and (C14 + Fe(α) + Fe23Zr6) and five two-phase fields (Fe(α) + C14), (Fe(α) + Fe23Zr6), (C15 + Fe23Zr6), (C15 + C14) and (Fe23Zr6 + C14) is proposed in the present work.

Macroscopic magnetic hardening due to nanoscale spinodal decomposition in Fe–Cr

The Fe–Cr alloy system is the basis of ferritic steels, which are important structural materials for many applications, including their use in future fusion reactors. However, when exposed to elevated temperatures and radiation, the Fe–Cr system can undergo phase separation, resulting in Fe-rich (α) and Cr-rich (α’) nanoscale regions. This in turn generates the so-called “475 °C embrittlement” and modifies the magnetic properties. The correlation between the microstructural and magnetic changes is however poorly understood, which currently prevents the possibility of assessing the material in a non-destructive way by magnetometry. Here, we study the microstructural decomposition of an Fe–40Cr alloy induced by annealing at 500 °C for extensive time scales and its impact on the magnetic properties using magnetometry and advanced experimental methods, such as atom probe tomography, transmission electron microscopy (TEM), and micromagnetic simulations. Upon annealing, the alloy rapidly exhibits a spinodal decomposition morphology with a typical length scale of about 10 nm. With increasing annealing time, the hardness assessed by Vickers testing, the magnetic saturation, and the coercivity increase, which correlates with an increase in α-volume fraction and the system's heterogeneity. The magnetic domain patterns imaged by TEM and interpreted with the help of micromagnetic simulations reveal at the nanometer scale the impact of decomposition on the magnetic response of Fe–Cr.

Structural and magnetic properties in the Heusler compounds Co3−x Fe x Al thin films

The structural and magnetic properties are important parameters for spintronic applications of Heusler compounds. The Co2FeAl and CoFe2Al alloys are considered as the representatives of the regular and inverse Heusler structure, respectively. Here, we present a systematic study of the structural and magnetic properties of Co3−x Fe x Al (x = 1 ∼ 2) Heusler thin films grown on MgO (001) substrates. The lattice parameters and magnetic properties, such as magnetic coercivity, saturated moment and four-fold magnetic anisotropy constant, display different change trends in the Co-rich and Fe-rich regions, which suggest that magnetic properties have relevance to the Heusler structures. Our findings give a better understanding of the Heusler structures and magnetic properties, which is helpful for developing spintronic applications.

X-Ray Studies of the Inverted Ejecta Layers in the Southeast Area of Cassiopeia A

The central strong activities in core-collapse supernovae are expected to produce the overturning of the Fe- and Si/O-rich ejecta during the supernova explosion based on multidimensional simulations. X-ray observations of the supernova remnant Cassiopeia A have indicated that the Fe-rich ejecta lies outside the Si-rich materials in the southeastern region, which is consistent with the hypothesis on the inversion of the ejecta. We investigate the kinematic and nucleosynthetic properties of the inverted ejecta layers in detail to understand its formation process using the data taken by the Chandra X-Ray Observatory. Three-dimensional velocities of Fe- and Si/O-rich ejecta are obtained as >4500 km s−1 and ∼2000–3000 km s−1, respectively, by combining proper motion and line-of-sight velocities, indicating that the velocity of the Si/O-rich ejecta is slower than that of the Fe-rich ejecta from the early stages of the explosion. To constrain their burning regime, the Cr/Fe mass ratios are evaluated as % in the outermost Fe-rich region and % in the inner Fe/Si-rich region, suggesting that the complete Si burning layer is invertedly located to the incomplete Si burning layer. All the results support the ejecta overturning at the early stages of the remnant’s evolution or during the supernova explosion of Cassiopeia A.

Study on FeCr thin film for a spintronic material with negative spin polarization

Negative spin polarization materials generate a spin current whose spin direction is opposite to the magnetization direction. This characteristic is technologically important because it increases the freedom in the design of spintronic devices. In this paper, we studied FeCr from the viewpoints of band structure, atomic magnetic moments, and local atomic arrangement to explore its potentiality as a negative spin polarization material. First-principles calculations on the disordered FeCr alloy predicted a high negative spin polarization, which was attributed to the band matching of the minority spin. We experimentally fabricated Fe1-xCrx thin films in the Cr concentration (x) range from 0.2 to 0.4 by sputter deposition and demonstrated inverse magnetoresistance using current-perpendicular-to-plane giant magnetoresistance (GMR) devices, which provided evidence of negative spin polarization. The spin polarization of Fe0.7Cr0.3 estimated from the GMR device measurements was −0.28 and fell below the calculated value. Synchrotron X-ray magnetic circular dichroism measurements showed a ferrimagnetic configuration of the Fe and Cr magnetic moments. The Fe moment showed a large moment over a wide Cr concentration range, whereas the Cr moment decreased with the Cr concentration, which agreed with the calculation result. Synchrotron Mössbauer spectroscopy measurements indicated the inhomogeneity of the FeCr composition even in the as-deposited state. Fe-rich regions were formed after annealing, reflecting the phase separation nature of the Fe-Cr system. Inhomogeneity was not considered in the calculation and could be the origin of the smaller negative spin polarization observed in the experiment.

Structural evolution and magnetic aspects in nanostructured (Fe92Zr8)96B4 alloys

Magnetic powder alloys (Fe92Zr8)96B4 were produced by using a combination of two synthesis techniques, casting and ball milling. Bulk samples were reached from casting while milling yield to powders to induce a homogenized structural phase. The structural analysis confirmed that initially an α-Fe phase (bcc) was formed with space group Im-3m. As the milling time goes from 0 to 36 h, small changes in the lattice parameter were noticed, going from 0.285 nm to 0.287 nm. Magnetic hysteresis loops measurements revealed that the samples are ferromagnetic at room temperature, with a maximum saturation magnetization ~ 161 emu/g for 0 h and~150 emu/g for 36 h. Likewise, the powder samples are magnetically soft at room temperature, with coercive field values below 50 Oe. Finally, through Mössbauer spectroscopy, the ferromagnetic character of the (Fe92Zr8)96B4 alloys was confirmed, where the hyperfine field sites can be associated with Fe-rich regions in which almost all the nearest neighbors are Fe atoms.

Phase relationships in the Fe-rich region of the Ce–Nd–B–Fe quaternary system at 773 K

Abstract The Fe-rich corner of the Ce–Nd–B–Fe quaternary system at 773 K has been experimentally investigated by means of X-ray powder diffraction and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy techniques. No quaternary compound was observed in this system. Ce2Fe14B and Nd2Fe14B were found to form the continuous solid solution (Ce,Nd)2Fe14B. Ce-Fe4B4 and NdFe4B4 also form the solid solution (Ce,Nd)-Fe4B4. The isothermal section consists of 8 three-phase regions and 2 four-phase regions.

Effect of Mg2+ coordination on the structural and optical properties of iron magnesium phosphate glasses

The O2− anions coordination by 3-5 of Mg2+ cations is the origin of Mg-rich cluster formation and photoemission properties of magnesium metaphosphate glasses. XRD, SAED and TEM analyses exhibit that Mg-rich clusters are of amorphous structure. The replacement of MgO by Fe2O3 results in the formation of crystalline Fe-rich regions. FTIR spectra reveal that Fe2O3 acts as network former and/or modifier by forming FeO4 and/or FeO6 groups, respectively. EDX mapping reveals that these Mg-rich clusters are disappeared at the expense of iron-rich clusters formation. UV-Vis absorption and fluorescence spectroscopies demonstrate that such coordination behavior is the reason for the photoemission of presented magnesium phosphate amorphous structure. Furthermore, replacement of Fe2O3 by MgO leads to photoemission quenching, which is assigned to the formation of Fe-rich clusters.