Atomic Number Of RE Research Articles

First-Principles Calculations on Relative Energetic Stability, Mechanical, and Thermal Properties of B2-AlRE (RE = Sc, Y, La-Lu) Phases

The relative energetic stability, mechanical properties, and thermodynamic behavior of B2-AlRE (RE = Sc, Y, La-Lu) second phases in Al alloys have been investigated through the integration of first-principles calculations with the quasi-harmonic approximation (QHA) model. The results demonstrate a linear increase in the calculated equilibrium lattice constant a0 with the ascending atomic number of RE, while the enthalpy of formation ΔHf exhibits more fluctuating variations. The lattice mismatch δ between B2-AlRE and Al matrix is closely correlated with the transferred electron et occurring between Al and RE atoms. Furthermore, the mechanical properties of the B2-AlRE phases are determined. It is observed that the calculated elastic constants Cij, bulk modulus BH, shear modulus GH, and Young’s modulus EH initially decrease with increasing atomic number from Sc to Ce and then increase up to Lu. The calculated Cauchy pressure C12-C44, Pugh’s ratio B/G, and Poisson’s ratio ν for all AlRE particles exhibit a pronounced directional covalent characteristic as well as uniform deformation and ductility. With the rise in temperature, the calculated vibrational entropy (Svib) and heat capacity (CV) of AlRE compounds exhibit a consistent increasing trend, while the Gibbs free energy (F) shows a linear decrease across all temperature ranges. The expansion coefficient (αT) sharply increases within the temperature range of 0~300 K, followed by a slight change, except for Al, AlHo, AlCe, and AlLu, which show a linear increase after 300 K. As the atomic number increases, both Svib and CV increase from Sc to La before stabilizing; however, F initially decreases from Sc to Y before increasing up to La with subsequent stability. All thermodynamic parameters demonstrate similar trends at lower and higher temperatures. This study provides valuable insights for evaluating high-performance aluminum alloys.

Nucleation and growth of L12-Al3RE particles in aluminum alloys: A first-principles study

The internal mechanisms of nucleation and growth of L12-Al3RE (RE = Sc, Y, La–Lu) second phases in Al alloys were investigated by combining first-principles calculations with quasi-harmonic approximation (QHA). The calculated results show that the diffusion rate Ds and chemical potential ΔGV increase with the increase of temperature. With the increase of atomic number, the Ds and the strain energy ΔECS increase firstly from Sc to La, and then decreases, while the calculated interface energy γα/β and ΔGV show opposite tendency. Based on above calculated results, the critical nucleation radius R∗ and coarsening rate KLSW are obtained from the classical nucleation theory (CNT) and LSW model of the Ostwald ripening of particles, respectively. With the increase of atomic number, the R∗ increases firstly, and then decreases for all planes at finite temperatures. Whereas the KLSW shows opposite variation to the R∗. From this point of view, it is reasonably speculated that Y and later RE elements can replace the expensive Sc for heat-resistance Al alloys. The solubility c∞ of particles is usually very small at low temperature, and there is obvious solubility only when the temperature reaches 600 K. The surface energies Esur of Al3RE compounds and Al solid solution are respectively larger and smaller than that of pure Al, respectively, except for the surface (001) and (110) of Al3La. For all planes, with the increase of atomic number of RE, Esur decreases firstly from Sc to La, and then increases linearly to Lu. These results are helpful for designing high performance heat-resistance Al alloys.

First-principles calculations of crystal structure, electronic structure and optical properties of Ba2RETaO6 (RE = Y, La, Pr, Sm, Gd)

The crystal structure, electronic structure and optical properties of Ba2RETaO6 (RE = Y, La, Pr, Sm, Gd) have been studied by first-principles calculation. The calculated lattice parameters are in good agreement with the previously reported values. With increasing the atomic number of RE (i.e., the number of 4f electrons), the energy level of RE 4f bands becomes lower continuously. The relationship between the electronic structure and optical properties is explored based on first-principles calculation. The electron transitions between O 2p states, RE 4f states and Ta 5d states have a key effect on optical properties such as dielectric function, refractive index, absorption coefficient and reflectivity. The phase structures have great influence on the optical properties of Ba2SmTaO6 and Ba2GdTaO6, and the big variation of reflectivity induced from phase transition makes them have potential applications in the infrared radiation protection area.

First-principle calculations of crystal structures, electronic structures, and optical properties of RETaO4 (RE = Y, La, Sm, Eu, Dy, Er)

It is an effective method to protect components from high power laser damage using high reflective materials. The rare earth tantalates RETaO4 with high dielectric constant suggests that they may have very high reflectivity, according to the relationship between dielectric constant and reflectivity. The crystal structures, electronic structures, and optical properties of RETaO4 (RE=Y, La, Sm, Eu, Dy, Er) have been studied by first-principle calculations. With the increasing atomic number of RE (i.e., the number of 4f electrons), a 4f electron shell moves from the bottom of conduction band to the forbidden gap and then to the valence band. The relationship between the electronic structures and optical properties is explored. The electron transitions among O 2p states, RE 4f states, and Ta 5d states have a key effect on optical properties such as dielectric function, absorption coefficient, and reflectivity. For the series of RETaO4, the appearance of the 4f electronic states will obviously promote the improvement of reflectivity. When the 4f states appear at the middle of the forbidden gap, the reflectivity reaches the maximum. The reflectivity of EuTaO4 at 1064 nm is up to 93.47%, indicating that it has potential applications in the antilaser radiation area.

Elastic and electronic properties of tI26-type Mg12RE (RE = Ce, Pr and Nd) phases

A detailed theoretical study of structural, elastic and electronic properties of tI26-type Mg12RE (RE = Ce, Pr and Nd) phases has been carried out by means of first-principles calculations based on density functional theory. The optimized lattice parameters at T = 0 K are in excellent agreement with the available experimental value at room temperature, and the obtained formation enthalpies show that with increasing atomic number of RE, the stability of Mg12RE alloys becomes lower. The elastic constants of tI26 Mg12RE are further calculated, then the bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν of polycrystalline aggregates are derived, and the relevant mechanical properties of Mg12RE alloys are also discussed. The elastic anisotropy of the three alloys is studied in detail using several methods, and the three-dimensional directional representation reveals the variation of Young's modulus along the crystallographic direction visually and completely. Finally, electronic density of states, charge density distribution and Bader charges are also calculated to reveal the underlying mechanism of structural stability and mechanical properties.

Impregnation synthesis of a novel macroporous silica-based TODGA polymeric composite and its application in the adsorption of rare earths in nitric acid solution containing diethylenetriaminepentaacetic acid

A macroporous silica-based N, N, N′, N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) polymeric composite (TODGA/SiO 2-P) was synthesized. It was done through impregnation and immobilization of TODGA molecule into the pores of the SiO 2-P particles utilizing a vacuum sucking technique. The macroporous SiO 2-P particles were the silica-based organic/inorganic composite synthesized by immobilizing styrene–divinylbenzene copolymer inside SiO 2 through the complicated polymerization reaction. The adsorption of rare earth (RE(III)) elements onto TODGA/SiO 2-P was investigated in HNO 3 solution containing diethylenetriaminepentaacetic acid (DTPA), an acidic multi-dentate chelating agent. It was found that in the presence of 0.05 M DTPA, NO 3 - and H + had significant effect on the TODGA/SiO 2-P adsorption due to the competition reactions of RE(III) with different species, H 4DTPA − and H 2DTPA 3−. With an increase in the concentration of NO 3 - from 0.115 M to 3.015 M, the adsorption of RE(III) onto TODGA/SiO 2-P increased noticeably. On the other hand, RE(III) showed strong adsorption at 0.1 M H +, weak adsorption at around pH 2, and no adsorption in excess of pH 2.3. In a 0.1 M H +–0.115 M NO 3 - –0.05 M DTPA solution, a change of the distribution coefficient of RE(III) onto TODGA/SiO 2-P with an increase in atomic number of RE(III) from La(III) to Lu(III) was investigated. The silica-based TODGA/SiO 2-P polymeric composite showed strong adsorption for heavy RE(III) over the light one. In a 0.01 M H +–1.0 M NO 3 - –0.05 M DTPA solution, the effect of the ratio of solid phase to liquid one on the relationship of the distribution coefficient of RE(III) with the change in atomic number of RE(III) was also studied. Based on the complicated disassociation equilibrium of DTPA, the influence of the concentrations of NO 3 - and H + on the adsorption of TODGA/SiO 2-P for RE(III) was demonstrated. This makes the partitioning of RE(III) and MA(III) together from high level liquid waste (HLLW) by the polymeric composite TODGA/SiO 2-P promising.

Synergistic Extraction of Rare Earths(III) with β-Diketone and Nitrogen-Containing Terdentate Ligand, 2,2′:6′,2″-Terpyridine

Abstract The synergistic extraction of rare earth(III) ions (RE: La, Sm, Tb, and Lu) was investigated using a β-diketone (HA), i.e., trifluoroacetylacetone (Htfa) or hexafluoroacetylacetone (Hhfa), in the presence of a terdentate ligand, 2,2′:6′,2″-terpyridine (terpy) into benzene. The formation of complexes such as RE(A)2+ or RE(A)2+ in the aqueous phase was observed. The synergistic enhancement is attributed to the formation of an adduct RE(A)3terpy in the benzene phase. The adduct formation constants (βS,1) and the synergistic extraction constants were determined. For each RE(III), the βS,1 value in the Htfa–terpy system is smaller than that in the Hhfa–terpy system. The βS,1 values decrease with increasing atomic number of RE(III) in the Htfa–terpy system, but the βS,1 value for La(III) is smaller than that for the other RE(III) in the Hhfa–terpy system.

Magnetic 3d-4f coupling in REBa 2Cu 3O 7−δ

We present specific heat and inelastic magnetic neutron scattering data on REBa 2Cu 3O 7−δ (Re = rare earth). Independent of the oxygen content drastic anomalies are observed in the temperature behaviour of the magnetic neutron scattering response. The quasielastic linewidth is nearly independent of temperature up to about 100 K and then increases linearly. Below T ≈ 100 K the quasielastic scattering changes continuously from Lorentzian to Gaussian character. Together with the systematic variation of the 4f ordering temperatures found by specific heat measurements this suggests an increase of an indirect 3d-4f coupling with decreasing atomic number of RE and could therefore also explain the anomalies in PrBa 2CuO 7−δ

57Fe Mössbauer Spectra Study on Eu0.5RE0.5Fe0.5Mn0.5O3 Oxides

AbstractThe method of solid state reactions is used to synthesize the samples of Eu0,5RE0,5Fe0,5Mn0,5O3 (RE = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y). XRD and 57Fe Mössbauer spectra are measured. It is found that the volume of the unit cell of the samples decreases with increasing atomic number of RE. The Fe ions are in the Fe3+ high spin state, and the relationship between the quadrupole splittings and the lattice distortion parameter D of the samples is linear.

Synergic extraction of rare earths with 2-thenoyltrifluoroacetone and phophoryl-type bidentate ligands such as tetraphenyldiphosphine dioxide or bis(diphenylphosphinyl) methane

The synergic extraction of rare earth(III) ions (RE; La, Sm, Tb and Lu) using 2-thenoyltrifluoroacetone (Htta) and phosphoryl-type uncharged bidentate ligands, such as tetraphenyldiphosphine dioxide (tpdpo) or bis(diphenyl-phosphinyl)methane (bdppm), was investigated in benzene. The synergic enhancement was attributed to the formation of the adduct RE(tta) 3S n ( n=1 or 2 for tpdpo and n=1 for bdppm) in benzene, where S denotes the uncharged ligand. The adduct formation constants (β S) and the synergic extraction constants were determined. For each RE(III), the β S,1 value for bdppm is larger than the β S,1 and β S,2 values for tpdpo and the β S values for both ligands decrease with increasing atomic number of RE(III).

Synergic Extraction of Rare Earths(III) with 4,4,4-Trifluoro-1-(2-thienyl)-1,3-butanedione and Nitrogen-Involving Polydentate Ligands as Diethylenetriamine and Triethylenetetramine

Abstract The synergic extraction of rare earths(III), i.e. La, Sm, Tb, and Lu, using 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Htta) and a nitrogen-involving neutral polydentate ligand, such as diethylenetriamine (dien) or triethylenetetramine (trien), was studied between benzene and aqueous phases. The synergic enhancement of this extraction system was attributed to the formation of an adduct, RE(tta)3dien or RE(tta)3trien. The adduct formation constants (βS,1) were determined. Although βS,1 decreases with the atomic number of RE(III), the detailed tendency of βS,1 depends on the number of nitrogen atoms of the polydentate ligands.

Adduct formation constant in the synergic extraction of several rare earth elements with acetylacetone and 1,10-phenanthroline in nonpolar organic solvents

The synergic extraction of La(III), Nd(III), Sm(III), Tb(III) and Lu(III) with 0.1M acetylacetone (Hacac) and 1,10-phenanthroline (phen) in benzene was studied. The adduct formation constant, βs, for RE(acac)3 (phen) in benzene was determined. The βs decreases with inceasing atomic number of RE(III). The βs in different organic solvents can be predicted in connection with the activity coefficients of the solutes, and the validity of this prediction is confirmed by good agreement with the experimental values of βs in carbon tetrachloride and heptane.

Thermoanalytical study on the reactions of selected rare earth oxides with ammonium halides

A comparative study has been made on the reactions of RE oxides (RE = Y, La, Gd and Lu) with ammonium bromide, and of yttrium oxide with ammonium halides NH 4X (X = F, Cl, Br and I) at different temperatures. Most of the reactions take place in three stages, with formation of two intermediate compounds, REX 3 · 3 NH 3 and REX 3 · 1.5 NH 3. The endothermic reactions begin between 200 and 300°C and the formation of the RE oxyhalide is completed between 340 and 470°C. These temperatures were observed to rise with the increasing atomic number of RE in the series LaOBrLuOBr, and of halide in the series YOFYOI.