X-ray Diffraction Rietveld Analysis Research Articles

Impact of Fe site Co substitution on superconductivity of Fe1-xCoxSe0.5Te0.5 (x = 0.0 to 0.10): A flux free single crystal study

We report synthesis of Co substitution at Fe site in Fe1-xCoxSe0.5Te0.5 (x=0.0 to 0.10) single crystals via vacuum shield solid state reaction route using flux free method. Single crystal XRD results showed that these crystals grow in (00l) plane i.e., orientation in c-direction. All the crystals possess tetragonal structure having P4/nmm space group. Detailed scanning electron microscopy (SEM) images show that the crystals are grown in slab-like morphology. The EDAX results revealed the final elemental composition to be near stoichiometric. Powder X-Ray diffraction (PXRD) Rietveld analysis results show that (00l) peaks are shifted towards higher angle with increasing Co concentration. Both a and c lattice parameters decrease with increasing Co concentration in Fe1-xCoxSe0.5Te0.5 (x=0.0 to 0.10) single crystals. Low temperature transport and magnetic measurements show that the superconducting transition temperature (Tc), decreases from around 12K to 10K and 4K for x=0.03 and x=0.05 respectively. For x=0.10 crystal superconductivity is not observed down to 2K. Electrical resistivity measurement of Fe0.97Co0.03Se0.5Te0.5 single crystal under magnetic field up to 14Tesla for H//ab and H//c clearly showed the anisotropy nature of superconductivity in these crystals. The upper critical field Hc2(0), being calculated using conventional one band Werthamer–Helfand–Hohenberg (WHH) equation, for x=0.03 crystal comes around 70Tesla, 45Tesla and 35Tesla for normal state resistivity criterion ρn=90%, 50% and 10% criterion respectively for H//c and around 100Tesla, 75Tesla and 60Tesla respectively for H//ab. The activation energy of Fe0.97Co0.03Se0.5Te0.5 single crystal is calculated with the help of TAFF model for both H//c and H//ab direction. In conclusion, Co substitution at Fe site in Fe1-xCoxSe0.5Te0.5 suppresses superconductivity.

Synthesis of a Bulk Ti4SiC3 MAX Phase by Reduction of TiO2 with SiC.

The bulk MAX phase Ti4SiC3 was first synthesized with a yield of 86% by a long-time thermal treatment of TiO2 and SiC powder mixture with a molar ratio of 2:3 at 1600 °C under vacuum conditions. It was found that the appearance of Ti4SiC3 was preceded by the formation of TiC and Ti3SiC2 as a result of the following reactions: (1) combined carbothermic and silicothermic reduction of TiO2 to TiC accompanied by evolution of SiO and CO gases; (2) silicidation of TiC with gaseous SiO, leading to the growth of Ti3SiC2. It was suggested that, apart from TiC and Ti3SiC2 solids, sublimed gaseous species such as Ti, Si, Si2C, SiC2, etc., could take part in the Ti4SiC3 formation that occurred in the next stage. The crystal structure of synthesized Ti4SiC3 was refined by X-ray diffraction Rietveld analysis and confirmed by high-resolution scanning transmission electron microscopy. The measured structural characteristics of bulk Ti4SiC3 are in good agreement with those predicted by ab initio calculations reported in the literature.

Traprock Transformation into Clayey Materials in Soil Environments of the Central Siberian Plateau, Russia

AbstractThe study of hard rock conversion into fine earths and clayey materials in the pedosphere is important in understanding the relative proportions of recent soil features to features that were inherited from ancient epochs. Cold environments are widely thought to be areas of physical weathering, but the coexistence of physical and chemical processes have also been shown. To further examine mafic rock (dolerite) weathering in soil environments and the conversion into clayey materials, Entic Podzols formed in the cold continental climate were studied. The key study was located in the central part of the flood basalt complex, or traps (traprocks), of the Central Siberian Plateau (Russia). The qualitative mineralogy was studied using X-ray diffraction and the quantitative mineral composition was determined using X-ray diffraction and subsequent Rietveld analysis. The micromorphological characteristics of the soils were studied in thin sections. Dolerite fragments and fine earths were sampled from soil profiles underlain by dolerite. XRD analyses indicated that pyroxene and especially plagioclase contents in the dolerite fragments and fine earths decreased from the bottom to the top soil horizons mostly in the mature soil profiles that were affected by chemical weathering of dolerite. The dioctahedral and trioctahedral smectites in the soils were inherited from a dolerite previously subjected to chemical weathering. The smectite was conserved in the inherited aggregates and protected against dissolution even in acidic soil horizons. Recent pedogenesis processes fractured individual fragments, converted it into soil micromass, and slightly decreased the total smectite content of the <1 µm soil fraction. However, in soil samples collected from the bottom to the top horizons of a mature soil profile, trioctahedral smectite contents decreased as dioctahedral smectite contents increased. This suggests that dioctahedral smectites formed by pedogenic alteration of inherited trioctahedral smectites.

Neutron diffraction studies on magnetic properties of Ca5Ni4V6O24

The temperature dependent neutron powder diffraction (NPD) and magnetization measurements of vanadium based garnet Ca5Ni4V6O24 (CNVO) have been performed to explore its crystal and magnetic structures. The magnetization results illustrate two magnetic anomalies at 7 and 4K. The Rietveld analysis of room temperature x-ray diffraction and NPD data confirms its Ia-3d crystal structure. The temperature dependent NPD shows the emergence of magnetic reflections below 7K whose intensity keeps on increasing with decreasing temperature down to 1.5K. The crystal structure remains cubic down to 1.5K. Rietveld analysis reveals that below 7K, the Ni moments in CNVO undergo a commensurate collinear A-type antiferromagnetic ordering with propagation vector k=(0,0,0) and the per site ordered moment of Ni2+ is 1.69±0.05μB. Absence of any additional magnetic or nuclear reflections below 4K confirms that the nuclear and magnetic structures remain invariant across the 4K magnetic anomaly.

Glassy Distribution of Bi3+/Bi5+ in Bi1–xPbxNiO3 and Negative Thermal Expansion Induced by Intermetallic Charge Transfer

The valence distribution and local structure of Bi1–xPbxNiO3 (x ≤ 0.25) were investigated by comprehensive studies of Rietveld analysis of synchrotron X-ray diffraction (SXRD) data, X-ray absorption spectroscopy (XAS), hard X-ray photoemission spectroscopy (HAXPES), and pair distribution function (PDF) analysis of synchrotron X-ray total scattering data. Disproportionation of Bi ions into Bi3+ and Bi5+ was observed for all the samples, but it was a long-ranged one with distinct crystallographic sites in the P1 triclinic structure for x ≤ 0.15, while the ordering was short-ranged for x = 0.20 and 0.25. An intermetallic charge transfer between Bi5+ and Ni2+, leading to large volume shrinkage, was observed for all the samples upon heating at ∼500 K.

Effect of 20% Cr-doping on structural and electrical properties of La0.67Ca0.33MnO3 perovskite

Structural and electrical properties of La0.67Ca0.33Mn1-xCrxO3 (x = 0 and 0.2) manganites are studied in this work. The samples were prepared using Pechini sol-gel method at 1173 K. Rietveld analysis of X-ray diffraction (XRD) patterns shows the formation of pure crystalline phase with orthorhombic Pnma structure with a decrease of the unit cell volume and crystalline domain size when increasing Cr-content. Electrical properties of the samples have been investigated using complex impedance analysis in 180–320 K temperature range with varying frequency between 40 and 106 Hz. For both samples, frequency dependence of imaginary part of impedance (Z″) shows the existence of relaxation phenomenon. The impedance study using Nyquist representation revealed the appearance of semicircle arcs and an equivalent circuit of the type of R1 + (R2//ZCPE) has been proposed to explain the impedance results. The conductance curves were analyzed by Jonscher power law and the deduced activation energy values are close to those calculated from relaxation time indicating that relaxation process and conductivity have the same origin.

Cation miscibility in KNO3[sbnd]RbNO3 binary system. A combined SEM, EDX and XRD Rietveld analysis

Phase relationships in the KNO3RbNO3 binary system at normal conditions were investigated by powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray analysis (EDX) techniques. The solubility limits in the solid state was determined. In the high potassium concentration domain, the solid solution K(1–x)RbxNO3 (denoted κ) crystallizes in the Pmcn orthorhombic symmetry were Rb+ may substitute K+ up to 52 mol %. For the solid solution Rb(1–y)KyNO3 (denoted ρ) in the rubidium rich zone the P31 trigonal symmetry is preferred and K+ may substitute Rb+ up to 24 mol %. Furthermore, the quantitative phase analysis (QPA) was performed for every sample leading to the amorphous and crystalline proportions. Refining the occupancy rates of every alkali cationic site in the solid solutions allows, not only the knowledge of the total cationic substitution rate in κ and in ρ phases but also the preferred crystallographic sites in every crystalline phase. These results were confirmed by microstructure investigations.

Cubic to tetragonal phase transition of Tm3+ doped nanocrystals in oxyfluoride glass ceramics

Tm3+ ions doped β-PbF2 nanocrystals in oxyfluoride glass ceramics with different doping concentrations and thermal temperatures are prepared by a traditional melt-quenching and thermal treatment method to investigate the structure and the phase transition of Tm3+ doped nanocrystals. The structures are characterized by X-ray diffraction Rietveld analysis and confirmed with numerical simulation. The phase transitions are proved further by the emission spectra. Both of the doping concentration and thermal temperature can induce an Oh to D4h site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm3+ doped nanocrystals at 800 nm was modulated by the phase transition of the surrounding crystal field.

Structural and Dielectric Properties of La0.33Sr0.67M0.33Ti0.67O3±δ (M = Mn or Fe) Perovskites

We have investigated the structural and dielectric properties of La0.33Sr0.67Mn0.33Ti0.67O3+δ (LSMTO) and La0.33Sr0.67Fe0.33Ti0.67O3−δ (LSFTO) perovskites synthesized by the solid-state reaction method at 1500 ∘C Rietveld analysis of X-ray diffraction (XRD) data shows pure crystalline phase with cubic \(Pm\bar {3}m\) structure, with no change in the unit cell volume due to the same ionic radii of Fe3+ and Mn3+. Scanning electron microscopy (SEM) micrographs show that the average grain size is slightly larger for LSMTO than for LSFTO. The electrical response of samples was studied at room temperature using the impedance spectroscopy technique over a broad frequency range (0.1Hz1MHz). The conductivity curves for the two samples were well fitted by the Jonscher law. For the LSFTO sample the hopping process occurs at long distance whereas for LSMTO compound, it occurs between neighboring sites. Variation of the dielectric parameter (e′) and that of the loss factor (e″) for both samples were explained by the different polarization and conductivity mechanisms. For both compounds, the variation of the imaginary part Z? shows a peak at a relaxation frequency (fr) related to the relaxation time (τ) by τ = 1/2πfr. Cole-Cole plots of impedance show the presence of two semicircles for LSMTO sample, whereas LSFTO compound shows one semicircle. To explain the impedance results, an appropriate electrical equivalent circuit has been proposed for each sample.

Experimental and theoretical characterization of ordered MAX phases Mo2TiAlC2 and Mo2Ti2AlC3

Herein, we report on the phase stabilities and crystal structures of two newly discovered ordered, quaternary MAX phases—Mo2TiAlC2 and Mo2Ti2AlC3—synthesized by mixing and heating different elemental powder mixtures of mMo:(3-m)Ti:1.1Al:2C with 1.5 ≤ m ≤ 2.2 and 2Mo: 2Ti:1.1Al:2.7C to 1600 °C for 4 h under Ar flow. In general, for m ≥ 2 an ordered 312 phase, (Mo2Ti)AlC2, was the majority phase; for m < 2, an ordered 413 phase (Mo2Ti2)AlC3, was the major product. The actual chemistries determined from X-ray photoelectron spectroscopy (XPS) are Mo2TiAlC1.7 and Mo2Ti1.9Al0.9C2.5, respectively. High resolution scanning transmission microscopy, XPS and Rietveld analysis of powder X-ray diffraction confirmed the general ordered stacking sequence to be Mo-Ti-Mo-Al-Mo-Ti-Mo for Mo2TiAlC2 and Mo-Ti-Ti-Mo-Al-Mo-Ti-Ti-Mo for Mo2Ti2AlC3, with the carbon atoms occupying the octahedral sites between the transition metal layers. Consistent with the experimental results, the theoretical calculations clearly show that M layer ordering is mostly driven by the high penalty paid in energy by having the Mo atoms surrounded by C in a face-centered configuration, i.e., in the center of the Mn+1Xn blocks. At 331 GPa and 367 GPa, respectively, the Young's moduli of the ordered Mo2TiAlC2 and Mo2Ti2AlC3 are predicted to be higher than those calculated for their ternary end members. Like most other MAX phases, because of the high density of states at the Fermi level, the resistivity measurement over 300 to 10 K for both phases showed metallic behavior.

The effect of Al on thermal stability and kinetics of decomposition of MgH2 prepared by mechanochemical reaction at different conditions

This work is directed at decreasing decomposition temperature of MgH2. In accordance with the theoretical predictions, hydride of solid solution of Al in Mg should decompose at lower temperature compared to that of MgH2, and numerous experiments indicate that thermodynamic stability of the hydride depends on methods and conditions of its synthesis. Therefore, the goal of this article is to study the possibility of obtaining the hydride of solid solution of aluminum in magnesium by different technological approaches. Three mechanical composite alloys derived by the different approaches are studied employing the X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermodesorption spectroscopy (TDS) methods. XRD Rietveld analysis reveals that the hydrogenation of a Mg + 10 wt% Al powder by means of reactive milling in the hydrogen atmosphere as well as hydrogenation of the powder from the gaseous phase after milling the powder for 20 h in the argon atmosphere leads to formation of aluminum-free MgH2 hydride and the Mg17Al12 phase. Our TDS studies (at PH2 = 0.1 MPa) indicate that additives of 10 wt% Al to magnesium do not lead to decreasing the decomposition temperature of MgH2 prepared by mechanochemical reaction at the different conditions.

Conduction mechanisms and enhanced multiferroic properties of Sr doped Bi0.85−xPr0.15SrxFe0.97Mn0.03O3 thin films

Pure BiFeO3 (BFO) and Bi0.85−xPr0.15SrxFe0.97Mn0.03O3 (BPSxFMO, x = 0.02–0.05) thin films were deposited on fluorine-doped SnO2 (FTO/glass) substrates by a sol–gel method. The systematic studies of crystalline structure, surface morphologies, leakage conduction mechanisms, ferroelectric and magnetic properties of pure BiFeO3 and Bi0.85−xPr0.15SrxFe0.97Mn0.03O3 thin films were investigated. X-ray diffraction patterns, Rietveld analysis and Raman scattering spectra reveal that the (Pr, Sr and Mn) co-doped BiFeO3 thin films give rise to a trigonal (R3m: R) structure transition with respect to the original rhombohedral structure of pure BiFeO3 film. Fowler–Nordheim tunneling conduction mechanism dominates the leakage current of all the films in the relatively high electric field. The significantly enhanced ferroelectric properties of the Bi0.85−xPr0.15SrxFe0.97Mn0.03O3 thin films were observed in comparison with pure BiFeO3 film. In addition, the BPS2FMO film shows the enhanced ferromagnetism with the saturation magnetization (Ms ~ 1.97 emu cm−3), which is almost three times larger than that of pure BFO film (Ms ~ 0.67 emu cm−3), as a result of the small grain size effect and the collapse of space modulated spin structure by the structure transition.

Crystal structure refinement, dielectric and magnetic properties of Sm modified BiFeO3 multiferroic

Bi1−xSmxFeO3 multiferroics (x=0.0, 0.05 and 0.1 having code BF0/SM0, SM5 and SM10 respectively) were synthesized via stage solid-state reaction method and their detailed structural, magnetic and impedance measurements are performed. X-ray diffraction profile and Rietveld analysis indicates that the crystal structure is rhombohedral (R3c). Due to Sm doping, the weak ferromagnetism in BiFeO3 ceramics may be attributed to the improved crystallinity and non presence of secondary phases. Bi0.9Sm0.1FeO3 ceramic exhibited the highest value of remnant magnetization and coercive field. The values of dielectric constant and dielectric loss of SM5 and SM10 samples showed dispersion at low frequency region. The temperature dependence of electric modulus at different frequencies shows the presence of well defined peaks and thus gives the temperature at which the measuring frequency is equal to conductivity relaxation frequency. The typical features of jump relaxation model are obeyed in ac conductivity analysis. Frequency dependence of the conductivity follows the universal power law.

A Study of the Composition, Distribution, and Genesis of Pyrrhotite In the Copper Cliff Offset, Sudbury, Ontario, Canada

Pyrrhotite (Po) from five orebodies (830, 865, 880, 890, and 100 OB) in the Copper Cliff Offset Dike (CCOD) at Sudbury, Ontario was studied using powder X-ray diffraction data and Rietveld analysis, SEM-EDS, magnetic colloid, optical petrographic techniques, and Laser Ablation-ICP-MS in order to: (1) quantify the distribution of NC (non-magnetic, symmetry higher than monoclinic) and 4C (magnetic, monoclinic in symmetry) Po; (2) characterize the major, minor, and trace-element chemistries of both polymorphs; and (3) determine the factors enhancing the stability of NC Po. Results confirm that both NC and 4C Po are present, with ratios varying between 0 to 0.97. In general, 4C Po is the dominant polymorph within the sampled OB, with the exception of the 100 OB, which is dominated by NC Po. Mineral chemistry indicates that there is an almost complete compositional overlap between the major, minor, and trace-element compositions of NC and 4C Po from the CCOD. The data also show that both polymorphs are slightly metal-deficient relative to the ideal chemistry of 4C Po, Fe7S8. There were no significant differences found in the Ni contents of either polymorph. Data revealed that the main mineralogical difference between the five OB was the presence of ilmenite in the 830, 865, 880, and 890 OB, whereas magnetite dominates in the 100 OB. Mineralization occurs along the eastern margin of the 830–890 OB, in contrast to the 100 OB, where mineralization occurs in the center of the dike. The increased abundance of NC Po in the 100 OB may be explained by this difference in the style of mineralization, specifically, the proximity of ore to the surrounding country rock. Therefore, f O2 may have directly influenced the distribution and stabilization of NC Po, which would then impact the observed NC:4C Po ratios in the selected OB.

New Insight into the Doping Effect of Pr2O3 on the Structure–Activity Relationship of Pd/CeO2–ZrO2 Catalysts by Raman and XRD Rietveld Analysis

Pd/CeO2–ZrO2–Pr2O3 (CZP) catalysts were synthesized with different Ce/Zr molar ratios and 8.0 wt % Pr2O3 doping. Their structures were characterized by various techniques, especially using X-ray diffraction (XRD) in combination with Rietveld refinement and Raman analysis. The XRD pattern of CZP with Ce/Zr molar ratios >1 can be indexed satisfactorily to the fluorite structure with a space group Fm-3m. When the Ce/Zr molar ratio reaches 1/2, the XRD patterns only display diffraction peaks of the tetragonal phase (S.G. P42/nmc). The Pr additive in the crystal lattice mainly replaces the position of Ce, which improves the redox reaction activity of catalysts when compared with Pr-free catalysts. Raman results reveal the enrichment of defect sites on the surface. The presence of moderate ZrO2 can increase both oxygen vacancies and the ZrO8-type complex in supports, which is in accord with the change regularity of their oxygen storage capacity (OSC) values. Moreover, the addition of moderate Zr and Pr promotes...

New PbTiO3-Type Giant Tetragonal Compound Bi2ZnVO6 and Its Stability under Pressure

A new PbTiO3-type compound, Bi2ZnVO6, with a giant tetragonal distortion of c/a = 1.26 (a = 3.7869(3) A, c = 4.7660(7) A) was synthesized under high pressure–high temperature conditions (9 GPa and 1373 K). A point charge model calculation based on the atomic positions refined by Rietveld analysis of synchrotron X-ray diffraction (SXRD) data gave an electrical ionic polarization of 126 μC/cm2, the largest value among PbTiO3-type perovskite compounds. The tetragonality (c/a) decreased with increasing temperature from 100 to 570 K without any trace of a phase transition. Instead, a pressure-induced transition from a polar tetragonal structure to a paraelectric GdFeO3 one accompanied by a 2.4% volume collapse was observed at 6.01 GPa. Bi2ZnVO6 showed paramagnetic behavior with S = 1/2 because of the random distribution of nonmagnetic Zn2+ and magnetic V4+ ions. Transport measurements indicated semiconductivity with an activation energy of 0.43 eV.

Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

The firing transformations of traditional (clay based) ceramics are of technological and archeological interest, and are usually reported qualitatively or semiquantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite), the low crystalline (metakaolinite and/or spinel type pre-mullite) and glassy phases evolution of a triaxial (clay-quartz-feldspar) ceramic fired in a wide temperature range between 900 and 1300 ºC. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 ºC) spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy) phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and materials properties. These correlations can be employed for materials characterization, design and processing control.

General study on the crystal, electronic and band structures, the morphological characterization, and the magnetic properties of the Sr2DyRuO6 complex perovskite

A comprehensive investigation of the general properties of the Sr2DyRuO6 complex perovskite was undertaken. Crystal structure characterization performed by X-ray diffraction measurements and Rietveld analysis allowed establishing that the material crystallizes in a distorted monoclinic perovskite-like structure belonging to the P21/n (#14) space group, with alternating distribution of Dy3+ (2c: 0, 0.5, 0) and Ru5+ (2d: 0.5, 0, 0). Because of the mismatch in the ionic radii, the DyO6 and RuO6 octahedra are forced to tilt around the cubic directions so as to optimize the Sr–O inter-atomic bond lengths. Morphological characterization carried out by scanning electron microscopy indicated a particle size D=37.17nm and an activation energy Q=109.8kJ/mol. Semi-quantitative compositional study, performed through energy-dispersive X-ray experiments, corroborated that the pure phase of the Sr2DyRuO6 was correctly obtained. Magnetic properties determined from the fit of the Curie–Weiss law to the curves of magnetic susceptibility as a function of temperature showed that Sr2DyRuO6 exhibits an antiferromagnetic-like behavior at low temperatures as a consequence of a magnetic transition at T=38K. Data collected with respect to the field dependence of the magnetization showed the existence of a weak ferromagnetic moment relationship with antiferromagnetic-like behavior. Density functional theory allowed establishing the optimum electronic structure for Sr2DyRuO6, and the study of the density of states showed that Dy3+ and Ru5+ are responsible for the magnetic character of the compound, with the prediction that at T=0K it behaves as a half-metallic material. The spin magnetic moment of the cell is close to 16μB, and the integer number of Bohr magneton is a signature of half-metallic character. Evolution of crystal structure at high temperature revealed that Sr2DyRuO6 does not undergo any structural phase transitions, since the Bragg reflections [hkl] do not undergo changes, and the structure is preserved.

Microstructure and mechanical properties of a new group of nanocrystalline medical-grade stainless steels prepared by powder metallurgy

This paper focuses on the structure and mechanical properties of powder metallurgy stainless steels (Fe–Cr–Mn–Mo–Si–N–C) developed for biomedical applications. The samples were prepared by mechanical alloying and subsequent liquid-phase sintering with a eutectic Mn–Si alloy additive. By changing the sintering aid content, the pore configuration, compressive strengths, and impact properties of the samples were assessed. The Rietveld X-ray diffraction analysis showed after sintering at 1050°C for 60min followed by water-quenching, a nanocrystalline austenitic structure was formed in the material. According to the mechanical experiments, by increasing the additive content from 0wt% to 6wt%, sintering densification, yield stress, compression strength, and absorbed impact energy were improved, where spoiling occurred when adding 8wt% additive. Also, as realized from the impact fracture surface features, despite the presence of some unmelted additive particles, the role of the pore elimination in toughness prevailed over that of these particles.

Magnetic and fluorescence properties of cerium-doped yttrium gadolinium aluminum iron garnet crystals

Magnetic and fluorescence properties of chemically synthesized Ce:Gd-YAIG (Ce0.05GdxY2.95−xAl5−yFeyO12) nanocrystals have been investigated. The structural characterization by X-ray diffraction (XRD) shows that a garnet phase has been identified in samples with 0 ≤ x ≤ 2.95 and 0 ≤ y ≤ 3.0. When y = 0, only garnet peaks are observed for 0 ≤ x ≤ 2.5, while both garnet and perovskite phases are present for x > 2.5. It is found from XRD Rietveld analyses that the site occupancy of Fe3+ at the tetrahedral and octahedral sites in the garnet is independent of the amount of Y3+ substituted by Ce3+ and Gd3+ at the dodecahedral sites. The saturation magnetization for the sample with x = 0 and y = 3.0 is 4.35 emu/g, while that with x = 2.5 and y = 3.0 is 87.5 emu/g. When the Fe3+ composition y is varied from 0 to 3.0 at x = 2.5, the intensity of fluorescence at the emission wavelength ∼570 nm significantly decreases presumably due to absorption by Fe3+ that is increased in the crystal.