Dy System Research Articles

Experimental investigation and thermodynamic modeling of the Al–Dy and Ni–Al−Dy systems

The partial phase equilibria of the Ni–Al−Dy ternary system have been systematically investigated via experimental analyses and thermodynamic modeling. Using the equilibrated alloy method, the 1150 °C and partial 800 °C isothermal sections of the Ni–Al−Dy ternary system and related Al–Dy binary system were constructed based on scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. Twelve three-phase regions were confirmed and four three-phase equilibria regions were speculated at 1150 °C, eight three-phase regions were determined at 800 °C, and five kinds of primary solidification regions, DyAl2, τ7, τ5, NiAl and Ni2Al3 were observed. A new ternary compound τ12 was discovered, which was stable at 800 °C and disappeared at 1150 °C, the τ1 phase was not stable at 800 and 1150 °C isothermal sections; the ternary compound τ11 was confirmed to be stable at 800 °C. In addition, the primary solidification phases were also identified, and five different primary solidification phases were found. Based on the experimental results available in this study and the literature, the thermodynamic modeling of the Ni–Al–Dy ternary system was obtained using the CALPHAD method. A set of self-consistent thermodynamic parameters for the Ni–Al–Dy ternary system was first obtained with a satisfactory agreement between the experimental and calculated results.

Reciprocating thermal behavior in the family of single ion magnets

Among the mononuclear transition metal and lanthanide complexes showing the slow magnetic relaxation, as a prerequisite of the single ion magnetism, there are examples of a non-traditional thermal behavior when at the low temperature the relaxation time, referring to the high-frequency relaxation channel, is shortened on further cooling instead of an expected prolongation. This reciprocating thermal behavior has been identified in a number of examples: for the Mn(II), Co(II), Ni(II), Cu(II), {Co(II)Co(III)}, {Gd(III)Ni(II)} and Dy(III) systems. The relaxation time in the low-temperature range can be recovered by applying equation τ–1 = CpbTl + FT–k where the phonon bottleneck process (rather than Raman process) and the “strange” process participate in the inverse relaxation time. The exponents of the temperature variable typically vary as l = 2–4 and k = 0.5–1.

Al–Cr–Dy system: Phase relationships and crystallography

The Al–Cr–Dy system has been investigated over the whole composition by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), scanning electron microscope and energy dispersion spectroscopy (SEM-EDS). The existence of known compounds Al8Cr4Dy and Al43Cr4Dy6 has been confirmed at 773 K. Binary compounds Al11Cr2 and Al17Dy2 do not exist in this isothermal section. The structure of the CeCr2Al20-type ternary compound Al20Cr2Dy has been determined with Rietveld refinement. This compound belongs to space group Fd3¯m and lattice parameter a = 1.44524 nm. The results shows that there are 16 single-phase regions, 31 two-phase regions and 16 three-phase regions in the studied isothermal section. The maximum solubility of Cr in AlDy2 and Al2Dy are confirmed to be 1.8 and 2.1 at. %, respectively. No significant solid solubility can be found in the other binary compounds of the Al–Cr–Dy ternary system at 773 K.

HF-Free Synthesis of α-Zirconium Phosphate and Its Use as Ion Exchanger for Separation of Nd(III) and Dy(III) from a Ternary Co–Nd–Dy System

The recovery of Nd and Dy from a ternary Co-Nd-Dy system using layered crystalline zirconium phosphate (alpha-ZrP) was investigated. alpha-ZrP was synthesized by the refluxing method, and subsequently characterized by sodium hydroxide titration, Fourier transform-infrared spectrometry, thermogravimetry, scanning electron microscopy, and X-ray diffraction. The selectivity and ion exchange kinetics of the alpha-ZrP material were determined with regard to the individual elements. The influence of solution pH on the uptake was studied in ternary 1 and 2 mM equimolar solutions. The results showed that in acidic solution (pH 1-3), very little Co was taken up, while Nd and Dy uptakes were at reasonable levels (0.5-0.6 meq/g). The uptake isotherms of Nd, Dy, and Co were measured separately at pH 2.5 and 4.5 in ternary equimolar solution series. At pH 4.5, the loading capacities were about 0.2 meq/g for Co, 1.1 meq/g for Nd, and 1.5 meq/g for Dy. Dy was thus clearly preferred over Nd by alpha-ZrP. The loading of an alpha-ZrP column showed a similar preferred pattern. Nitric acid eluent removed Co, Nd, and Dy, but there was no separation of the metals in the eluate. A mixture of nitric and phosphoric acids, however, produced a strong separation. Co was very weakly retained in the column, and the ratio Dy/Nd in the eluent was in the range of 2-7. Thus, the alpha-ZrP material showed encouraging ion exchange properties for the separation and recycling of Nd and Dy from a ternary Co-Nd-Dy system. Much more work is needed, however, to develop a practical separation flowsheet.

Thermodynamic reassessment of the Au–Dy system supported by first-principles calculations

Based on the available experimental phase equilibria and thermodynamic data and enthalpies of formation computed via first-principles calculations, thermodynamic reassessment of the Au–Dy system was carried out by means of the CALPHAD method. The enthalpies of formation at 0K for AuDy2, αAuDy, βAuDy, Au2Dy, Au3Dy, Au51Dy14 and Au6Dy were computed via first-principles calculations to supply the necessary thermodynamic data for the modeling in order to obtain the thermodynamic parameters with sound physical meaning. The solution phases, i.e. liquid, (Au), (αDy) and (βDy), were described by the substitutional solution model, and all the intermetallic compounds in the Au–Dy system were treated as stoichiometric phases. A set of self-consistent thermodynamic parameters for the Au–Dy system was finally obtained. The calculated phase diagram and thermodynamic properties agree reasonably with the literature experimental data and the present first-principles calculations.

Joint solubility of samarium and dysprosium in solid magnesium

The phase compositions of solid Mg–Sm–Dy alloys corresponding to the magnesium-corner region of the phase diagram are studied by optical and scanning electron microscopy, electrical resistivity measurements, and electron microprobe analysis. The obtained results allowed us to determine the joint solubility of samarium and dysprosium in solid magnesium at 500, 400, and 300°C; it decreases with decreasing temperature. The magnesium solid solution is found to be in equilibrium only with the Mg41Sm5 and Mg24Dy5 compounds, which are in equilibrium with the magnesium solid solution in the binary Mg–Sm and Mg–Dy systems.

Microstructure and Properties of Nd – Fe – B Alloys Produced by Strip Casting and of Permanent Magnets Fabricated from Them

Optimization of the microstructure of plates from alloys of the R – Fe – B (R: Nd, Dy) system obtained by pouring the melt onto a rotating copper drum by the method of strip casting is studied. The strip-cast Nd – Fe – B and Nd – Dy – Fe – B alloys with optimized microstructure are used to produce high-energy and high-coercivity sintered magnets.

Down- and up-conversion of femtosecond light pulse excitation into visible luminescence in cerium-doped Lu(2)SiO(5)-Gd(2)SiO(5) solid solution crystals co-doped with Sm(3+) or Dy(3+).

Luminescence phenomena following femtosecond pulse excitation in UV and IR of Ce(3+) + Sm(3+) and Ce(3+) + Dy(3+) systems in Lu(2)SiO(5) - Gd(2)SiO(5) single crystals are investigated. Effect of excitation wavelength in the UV on Ce(3+) luminescence is interpreted assuming selective excitation of weakly interacting Ce1 and Ce2 sites. IR-excited up-converted spectra differ as compared to UV-excited spectra in that the contribution of Sm(3+) or Dy(3+) luminescence is higher and the Ce(3+) luminescence originates essentially in Ce1 sites. It has been concluded that excitation mechanism of up-conversion involves energy transfer from free electrons created in conduction band of the host.

Critical thermodynamic evaluation and optimization of the Pb–Pr, Pb–Nd, Pb–Tb and Pb–Dy systems

All available experimental data on phase equilibria and thermodynamic properties of the Pb–Pr, Pb–Nd, Pb–Tb and Pb–Dy binary systems were reviewed and critically examined. A thermodynamic optimization of these systems is presented for the first time. A set of optimized model parameters for all solid stoichiometric compounds, terminal solid solutions and liquid phase was built to reproduce all available reliable thermodynamic properties and phase diagram data within experimental error limits. The Modified Quasichemical Model in the pair approximation was used to describe the thermodynamic properties of the liquid solution accurately. In view of the limited experimental phase diagram and thermodynamic data available for these systems, trends in the rare earth-lead and rare earth–tin systems were examined to estimate the missing information and evaluate whether the predictions are reasonable. Based on these trends, a predicted phase diagram for the Pb–Nd and Pb–Tb systems, which are not established to date, is presented.

Thermodynamic assessment of the Bi–Er and the Bi–Dy systems

Based on the available experimental data, the Bi–Er and the Bi–Dy binary systems have been assessed thermodynamically using the CALPHAD (CALculaton of PHAse Diagram) technique. The formation enthalpies at 0K of the compounds, Bi3Er5, BiEr, Bi3Dy5 and BiDy, were calculated by the first-principles method and Birch–Murnaghan equation of state, and the calculated results were used in the present thermodynamic optimization. All these compounds in the Bi–Er and the Bi–Dy systems were treated as stoichiometric compounds. The liquid phase was modeled as a substitutional solution phase based on random mixing of the constituent atoms and the excess Gibbs energy was formulated with the Redlich–Kister polynomial. Good agreements were obtained between the calculated results and the experimental data for both the thermochemical properties and the phase equilibrium relations.

Synthesis, structures and magnetic characterizations of isostructural tetranuclear Ln4 clusters (Ln = Dy, Ho, and Eu)

Isostructural tetranuclear clusters [Ln4(salen)6]·xH2O [Ln = Dy, 1·5.5H2O; Ho, 2·4.6H2O; Eu, 3·5.2H2O; salen = N,N'-ethylenebis(salicylideneiminato)dianion] were prepared by self-assembling the corresponding lanthanide ions and a quadridentate Schiff base. Interestingly, the Ln ions are surrounded by the N- and O-donors of the Schiff bases, leading to seven- and eight-coordinate environments. The heptacoordinated Ln centers adopt a distorted capped trigonal prism, while the octacoordinated Ln atoms are in a dodecahedral disposition. The Dy complex exhibits slow magnetic relaxation, characteristic of a single-molecule magnet. Two relaxation modes in the Dy system are evident when H(dc) = 1.4 kG is applied, which is attributable to the existence of the dissimilar coordination geometries around Dy. In comparison, the Ho and Eu analogues were magnetically inspected, displaying no typical slow magnetic relaxation. These findings elucidate that the metal component in the system plays a central role in the occurrence of the magnetization relaxation process. The pronounced long-range order may contribute to intrachain exchange couplings and through-space dipolar interactions between adjacent chains.

Experimental determination of the phase relations of the Co–Pt–Dy system at 773 K

The isothermal section of the Co–Pt–Dy system at 773 K was experimentally determined by combining results from X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy investigations. The presence of Co3Dy4 phase at 773 K is confirmed in this study. The four-phase region does not exist at 773 K in the ternary Co–Pt–Dy system, with instead two three-phase regions consisting of Co, DyPt, Dy3Pt4 and Co, DyPt2, Dy3Pt4, respectively. 23 single-phase regions (including solid solution regions of the binary compounds) and 21 three-phase regions were identified to exist at this isothermal section. The highest solid solubility of Dy in α1(Co, Pt), ∊(Co, Pt), α2(Co, Pt), CoPt, CoPt, α(Pt, Co) is less than 1.5 at.% Dy and that of Co in Dy3Pt, Dy2Pt, Dy5Pt3, Dy5Pt4, DyPt, Dy3Pt4, DyPt3, DyPt5 is below 1 at.% Co. The DyPt2 phase dissolves up to about 19 at.% Co. The maximum solid solubility of Pt in Co2Dy, Co3Dy, Co7Dy2, Co17Dy2 is approximately 1 at.% Pt. No new binary and ternary phases were found.

A Linear 3d–4f Tetranuclear CoIII2DyIII2 Single‐Molecule Magnet: Synthesis, Structure, and Magnetic Properties

A linear tetranuclear 3d-4f Co(2) Dy(2) cluster assembled from a polydentate Schiff base exhibits single-molecule magnet (SMM) behavior with an anisotropic barrier of 33.8 K. Due to the presence of diamagnetic cobalt(III) ions, the tetranuclear cluster of 1 behaves magnetically like a dinuclear Dy(2) system. However, the diamagnetic segment might efficiently minimize undesirable intermolecular magnetic interactions, thereby improving the performance of the SMM behavior of 1. This discrete complex presents us with a unique opportunity to study the magnetic properties and to probe the dynamics of magnetization in a magnetically isolated Dy(2) system.

Study of effect of mechanical deformation on thermoluminescence of gamma-ray-irradiated Dy doped MgSO4 phosphors

Abstract In order to find the mechanical stability of traps/luminescence centers responsible for TL in MgSO 4 :Dy system, effect of deformation on TL of MgSO 4 :Dy was studied. TL glow curve of MgSO 4 :Dy phosphor is complex and peaks around 110, 150 and 220 °C were observed. Optimum TL was obtained for the sample having 0.1 mol% concentration of Dy in MgSO 4 system. Slight increase in intensity of 110 °C peak was observed when the TL glow curve was recorded after deforming the irradiated samples by dropping a piston of mass 0.4 kg onto it from the height of 0.2 m. Further increasing the height from which the piston was being dropped TL peak intensity of 110 °C decreased. However, 150 °C and 220 °C TL peak intensity decreased with deformation. Result showed that trap centers associated with 150 °C and nearby TL peaks were most mechanically unstable. TL spectrum of MgSO 4 :Dy phosphors was also recorded. Two peaks one at 490 nm and another at 590 nm were observed. In the TL emission spectra recorded for deformed samples, no significant change was seen in the peak positions. However, peak intensity was reduced. It is suggested that the recombination of electrons released from the traps during the thermal excitation is responsible for the TL emission in this system. It seems that in MgSO 4 :Dy system deformation does not cause any appreciable change in the recombination mechanism, it causes redistribution of traps and therefore change in relative TL intensity occurs in the same spectral region.

Thermodynamic and ab initio investigation of the Cu–Dy system

A combined ab initio and thermodynamic study of the Cu–Dy system has been performed and a self-consistent thermodynamic database has been obtained. Density functional theory has been applied by using the VASP code in order to obtain the enthalpy of formation at 0 K of intermetallic compounds. Experimental information on the Cu–Dy phase diagram and thermodynamic properties of its alloys have been collected. Using these data, optimized parameters have been obtained by applying the CALPHAD approach. The present results reproduce the experimental data available reasonably well, although some features of the Cu–Dy system need to be further clarified.

Thermodynamic assessment of Al–Cu–Dy system

Phase equilibria of ternary Al–Cu–Dy system has been analyzed and a complete thermodynamic description was obtained. The thermodynamic descriptions of its three constituent binary systems were taken from literature. Most of the binary intermetallic phases, except Al 2Dy, Cu 2Dy, and CuDy, were treated to have zero solubility in ternary system. Based on experimental data, seven stable ternary intermetallic phases were taken into consideration in this system. Among them, three were treated as semistoichiometric compounds with large homogeneity ranges for Al and Cu. The rest were treated as stoichiometric compounds. The calculated phase equilibria were in agreement with available experimental data.

Phase Equilibria in the Sc2S3-Ln2S3 (Ln = Dy, Er, or Tm) Systems

Phase diagrams for the Sc2S3-Ln2S3 (Ln = Dy, Er, or Tm) systems were designed in the range from 1000 K to melting temperatures. The Ln3ScS6 compounds that are formed in these systems crystallize in monoclinic space group P21/m, and melt congruently: for Dy3ScS6, a = 1.118 nm, b = 1.262 nm, c = 0.354 nm, β = 94.7°, 1800 K, H = 2600 MPa; for Er3ScS6, a = 1.113 nm, b = 1.258 nm, c = 0.353 nm, β = 94.5°, 1830 K, H = 2800 MPa; for Tm3ScS6, a = 1.112 nm, b = 1.229 nm, c = 0.352 nm, β = 94.3°, 1835 K, H = 2940 MPa. The LnScS3 (Ln = Dy or Er) complex sulfides, with orthorhombic structures, space group Pnma, melt incongruently: for DyScS3, a = 0.700 nm, b = 0.637 nm, c = 0.943 nm, 1810 K, H = 3800 MPa; and for ErScS3, a = 0.697 nm, b = 0.633 nm, c = 0.942 nm, 1800 K, H = 3800 MPa. As the ionic radii rLn3+ and rSc3+ approach Ln Sc to each other in the row Dy-Er-Tm, the solubility in Sc2S3 increases, at 1670 K being equal to 13 mol % Dy2S3, 30 mol % Er2S3, and 40 mol % Tm2S3. LnScS3 (Ln = Dy or Er) forms a two-sided homogeneity region, at 1670 K lying in ranges of 43–56 mol % Ln2S3. The eutectic temperatures and compositions are as follows: 1700 K and 66 mol % Dy2S3, 1730 K and 81 mol % Dy2S3, 1740 K and 65 mol % Er2S3, 1700 K and 83 mol % Er2S3, 1730 K and 70 mol % Tm2S3, and 1755 K and 84 mol % Tm2S3.

Synthesis of the Bi-2222 Compounds of Bi–Sr–Ln(Zr)–Cu–O (Ln = Sm, Eu, Gd, and Dy)

Bi-based superconducting compounds with the 2222 structure has been already synthesized in the Bi2Sr2- (Ln1−xCex)2Cu2O10+y (Ln = Sm, Eu, and Gd) systems. One of the characteristics of these compounds is the existence of the fluorite-like (Ln1−xCex)2O2 block between two CuO5 pyramids in the crystal structure. The tetravalent ions of Ce4+ are reported to be necessary to stabilize the 2222 structure. Recently, we have discovered that the Bi-2222 phase could be composed in the Bi2Sr2(Ln2−xZrx)Cu2Oz (Ln = Sm, Eu, Gd, and Dy) systems, where Zr4+ is used as a new tetravalent ion stabilizing the 2222 structure in stead of Ce4+. In the new system, nearly single 2222 phase samples have been obtained at the nominal composition of x=0.5 (Ln = Sm, Eu, and Gd) and in the range of 0.1≤x≤0.3 (Ln = Dy). Among them, the sample with Ln = Gd has the smallest resistivity at 273 K. But it is a semiconductor, and the conduction process at low temperatures is assumed to be followed by a two-dimensional VRH. The experimental results for the Gd samples with a partial substitution of Pb for Bi in the Bi2Sr2(Gd2−xZrx)Cu2Oz system are also reported.

The influence of oxygen pressure on phase equilibria in the Ln-Mn-O (Ln = Sm, Tb, Dy, Yb, and Lu) systems

The influence of oxygen pressure on phase equilibria during thermal dissociation in the Ln-Mn-O (Ln = Sm, Tb, Dy, Yb, and Lu) systems was studied by the static method on a vacuum circulation unit with subsequent X-ray analysis of quenched solid phases. The reduction of the double oxides was found to occur according to the reactions LnMn2O5 = LnMnO3 + (1/3)Mn3O4 + (1/3)O2, LnMnO3 = (1/2)Ln2O3 + MnO + (1/4)O2, for which the temperature dependences of equilibrium oxygen pressure were determined over the temperature range 973–1220 K. The Gibbs energies of dissociation of the double oxides were calculated. Interrelation between the type of lanthanides and the thermal properties of the compounds was analyzed.

Defect centres and thermoluminescence in CaSO4:Dy,Ag phosphor

The defect centres formed in the TL phosphor CaSO4:Dy,Ag are studied using the technique of Electron Spin Resonance. The Ag co-doped phosphor exhibits three glow peaks around 130, 220 and 375 degrees C in contrast with the two glow peaks observed in the CaSO4:Dy phosphor at 130 and 220 degrees C at a gamma ray dose of 1Gy. ESR studies show that the additional peak at 375 degrees C correlates with a Ag2+ centre formed due to gamma irradiation and observable only below -170 degrees C. The Ag2+ centre is characterised by an axial g-tensor with principal values g(parallel) = 2.38 and g(perpendicular) = 2.41. ESR studies further indicate that the precursor to a centre observable at low temperature (-170 degrees C) appears to act as the recombination centre for the TL peak at 375 degrees C; this radical is characterised by the g-values g(parallel) = 2.0023 and g(perpendicular) = 2.0038 and is assigned to SO3- radical. It is observed that there is more incorporation of Ag in the CaSO4:Dy system as compared with that in pure CaSO4 system.